Created on 20150727.11:45:19 by silvan, last changed by silvan.
Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1 => issue851). Some ideas on how to further improve
performance can be found in the summary of issue851.
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849)
S. Let the mergeandshrink heuristic filter "trivial factors" when the mergeandshrink algorithm terminates with more than one factor (through imposing a time limit). A factor is trivial iff all of its states are goal states and the corresponding mergeandshrink representation is a total function. (issue914)

msg8965 (view) 
Author: silvan 
Date: 20190926.14:21:17 

Add item S:
Let the mergeandshrink heuristic filter "trivial factors" when the mergeandshrink algorithm terminates with more than one factor (through imposing a time limit). A factor is trivial iff all of its states are goal states and the corresponding mergeandshrink representation is a total function.

msg8392 (view) 
Author: silvan 
Date: 20181218.16:32:50 

Add a note to item J about further possible ideas for improvements that are
leftover from issue851.

msg7853 (view) 
Author: malte 
Date: 20181003.16:25:25 

Actually, what I made item S was already in the list as item J. I have removed
the item and instead added a pointer to the relevant issue851 to item J.

msg7852 (view) 
Author: malte 
Date: 20181003.16:24:01 

Add item S.

msg7832 (view) 
Author: silvan 
Date: 20181002.18:56:09 

Add issue802 to item E. Add item R.

msg7175 (view) 
Author: silvan 
Date: 20180604.18:26:05 

Extend item C to further investigate making label reductions faster more
generally, e.g. through using different algorithms and data structures for label
equivalence relations.

msg7162 (view) 
Author: silvan 
Date: 20180604.14:19:19 

Add new action item (quoted from Malte @ issue668).

msg7065 (view) 
Author: silvan 
Date: 20180422.14:24:34 

Change item letter.

msg6428 (view) 
Author: silvan 
Date: 20170709.15:18:20 

Item N is resolved with issue707.

msg6381 (view) 
Author: silvan 
Date: 20170519.14:26:05 

In the meantime, issue722 adapted the interface of FTS to better mimic the
concepts of applying transformations to it. There is no prune transformation
from outside yet, but issue707 will likely deal with this.

msg6146 (view) 
Author: silvan 
Date: 20170220.15:32:37 

issue707 will deal address item N.

msg5937 (view) 
Author: silvan 
Date: 20161220.15:22:19 

In issue682, we dealt with item M.

msg5579 (view) 
Author: silvan 
Date: 20160823.14:55:35 

issue666 makes ShrinkStrategy::shrink virtual to ease combining different shrink
strategies. It also introduces an iterator for FactoredTransitionSystem.

msg5570 (view) 
Author: silvan 
Date: 20160819.12:21:01 

The new design for merge strategies which eases plugging together different
types of merge strategies is in place (issue644).

msg5479 (view) 
Author: silvan 
Date: 20160726.16:57:18 

issue658 introduced creating merge strategies from factories.

msg5334 (view) 
Author: silvan 
Date: 20160511.13:46:06 

issue655 deals with simplifying the interface of shrink strategies.

msg4980 (view) 
Author: silvan 
Date: 20151214.11:25:29 

Items B and O, the separation of TransitionSystem into several parts and a
oneshot creation with FTSFactory can be considered done with issue604.

msg4934 (view) 
Author: silvan 
Date: 20151210.11:32:08 

H. has been addressed in issue599.

msg4882 (view) 
Author: silvan 
Date: 20151207.10:49:19 

issue601 has been merged: label reduction was moved back to its own file, and
FactoredTransitionSystem was refactored further.

msg4836 (view) 
Author: silvan 
Date: 20151126.13:27:56 

A few new action items from an old email:
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. FTSFactory
 We currently have a twostage initialization for the atomic
transition systems. First, they are created in an incomplete state,
and then the factory takes over the rest of the initialization. We
should have a constructor that generates them in one shot.

msg4790 (view) 
Author: silvan 
Date: 20151113.16:36:46 

issue595 addresses a bug in DFP and will also refactor it.

msg4779 (view) 
Author: silvan 
Date: 20151112.09:26:35 

issue583 has been merged. Item B, "splitting TransitionSystem" into several
parts, can be considered done, but the new class FactoredTransitionSystem still
allows further improvements.

msg4577 (view) 
Author: silvan 
Date: 20150812.14:03:16 

issue571 has been merged. There is still more to do in the spirit of item B).

msg4522 (view) 
Author: silvan 
Date: 20150728.17:56:42 

See issue571 for the next steps of item B).

msg4517 (view) 
Author: malte 
Date: 20150728.15:05:06 

Some additional items:
H. Introduce a namespace for mergeandshrink.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
L. TransitionSystem::get_init_distance() and
TransitionSystem::get_goal_distance() should disappear; instead the Distances
object should be asked directly. This should be an inlinable code path (msg4467,
msg4468).

msg4516 (view) 
Author: malte 
Date: 20150728.15:04:05 

Let's assign some letters to the action items we have mentioned so far:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.

msg4485 (view) 
Author: malte 
Date: 20150727.11:53:50 

Two additional notes that I made when we recently read the IJCAI 2015 paper on
simulation in M&S by Álvaro and Jörg:
 They use a "max_transitions" limit to control M&S generation. (See Section 8,
second paragraph.) It would be useful for us to implement this. The transitions
are harder to control than the states, but they are also more important. (They
use this to abort the construction process, rather than to control how much to
shrink. If we copy this behaviour, perhaps the name should be sufficiently
distinguished from max_states etc. to make this clear.)
 There are cases where exact label reduction is possible even though the two
labels have different cost. Perhaps we want to look into this.

msg4483 (view) 
Author: silvan 
Date: 20150727.11:45:19 

This meta issue is the continuation of issue432, to have a clean overview of all
upcoming issue which are due to code reviewing.
To start off, these are the open issues left over from issue432:
 issue415: better memory management
 issue561: split off TransitionSystem into several parts
Further three comments from an old refactoring list, although unclear if they
are going to be addressed:
 TransitionSystem::compute_local_equivalence_relation():
make computation faster through sorting transitions (O(n log n)) or hashing
(O(n)). Sorting is probably better, because we do not need to consider all
transitions in the best case.
 Add a hybrid bisimulation/greedy bisimulation strategy, inspired from
the code used for the IJCAI 2011 paper. See also issue431.
 Add a max_time parameter similar as in iPDB.


Date 
User 
Action 
Args 
20190926 14:21:17  silvan  set  messages:
+ msg8965 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1 => issue851). Some ideas on how to further improve
performance can be found in the summary of issue851.
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849) > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1 => issue851). Some ideas on how to further improve
performance can be found in the summary of issue851.
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849)
S. Let the mergeandshrink heuristic filter "trivial factors" when the mergeandshrink algorithm terminates with more than one factor (through imposing a time limit). A factor is trivial iff all of its states are goal states and the corresponding mergeandshrink representation is a total function. (issue914) 
20181218 16:32:50  silvan  set  messages:
+ msg8392 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1 => issue851).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849) > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1 => issue851). Some ideas on how to further improve
performance can be found in the summary of issue851.
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849) 
20181003 16:25:25  malte  set  messages:
+ msg7853 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849)
S. more efficient computation of transitions of irrelevant operators (issue851) > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1 => issue851).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849) 
20181003 16:24:01  malte  set  messages:
+ msg7852 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849) > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849)
S. more efficient computation of transitions of irrelevant operators (issue851) 
20181002 18:56:09  silvan  set  messages:
+ msg7832 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing. > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB. (issue802)
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing.
R. Separate the mergeandshrink computation from the heuristic. (issue849) 
20180604 18:26:05  silvan  set  messages:
+ msg7175 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing. > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
More generally, investigate different algorithms and data structures for
computing local equivalence relations to potentially further accelerate the
computation of label reductions. It would be useful to analyze which parts of
label reductions are bottlenecks of the computation.
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing. 
20180604 14:19:19  silvan  set  messages:
+ msg7162 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors).
Q. Mergeandshrink should internally use separate plugins like we do in other
cases, too; it is not really in keeping with the overall component architecture
for mergeandshrink to be all or nothing. 
20180422 14:24:34  silvan  set  messages:
+ msg7065 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
L. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
P. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors). 
20180314 18:05:44  silvan  set  summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
L. The current design of merge strategy factories is a bit flawed: they require
knowledge about the task (its variables, in case of linear merge strategies; or
the causal graph, in case of hybrid strategies like the SCC framework). In
particular, using merge trees (and their factories) within hybrid strategies is
not easily possible without storing further knowledge on the task, such as which
variables are contained in which components. We want to discuss this issue and
come up with a better design that matches our view
of factored transition systems consisting of variables (the factors). 
20170709 15:18:20  silvan  set  messages:
+ msg6428 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2). 
20170519 14:26:05  silvan  set  messages:
+ msg6381 
20170220 15:32:38  silvan  set  messages:
+ msg6146 
20161220 15:22:19  silvan  set  messages:
+ msg5937 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). 
20160823 14:55:35  silvan  set  messages:
+ msg5579 
20160819 12:21:01  silvan  set  messages:
+ msg5570 summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. merge strategies:
 improve interface and make a distinction between precomputed and
nonprecomputed merge strategies (issue644) > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). 
20160726 16:57:18  silvan  set  messages:
+ msg5479 
20160511 13:46:06  silvan  set  messages:
+ msg5334 
20160406 18:45:17  silvan  set  summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. merge strategies:
 improve interface and make a distinction between precomputed and
nonprecomputed merge strategies (issue644) 
20160217 12:17:54  silvan  set  summary: Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431. This strategy is
also discussed in the ICAPS 2012 paper.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). 
20151214 11:25:29  silvan  set  messages:
+ msg4980 summary: Open action items:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. FTSFactory
 We currently have a twostage initialization for the atomic
transition systems. First, they are created in an incomplete state,
and then the factory takes over the rest of the initialization. We
should have a constructor that generates them in one shot. > Open action items:
A. issue415: better memory management
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector). 
20151210 11:32:08  silvan  set  messages:
+ msg4934 summary: Open action items:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
H. Introduce a namespace for mergeandshrink.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. FTSFactory
 We currently have a twostage initialization for the atomic
transition systems. First, they are created in an incomplete state,
and then the factory takes over the rest of the initialization. We
should have a constructor that generates them in one shot. > Open action items:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. FTSFactory
 We currently have a twostage initialization for the atomic
transition systems. First, they are created in an incomplete state,
and then the factory takes over the rest of the initialization. We
should have a constructor that generates them in one shot. 
20151207 10:49:19  silvan  set  messages:
+ msg4882 
20151126 13:28:11  silvan  set  summary: Open action items:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
H. Introduce a namespace for mergeandshrink.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2). > Open action items:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
H. Introduce a namespace for mergeandshrink.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2).
M. heuristic representation:
 The class that is currently called HeuristicRepresentation doesn't
represent the heuristic. It represents the abstraction. Suggestion:
rename it to MergeAndShrinkRepresentation, which is the name we use
in our ICAPS 2015 paper.
 We currently have a twostage heuristic lookup process: map the
concrete state to an abstract state, then map the abstract state to
a cost value. The second step is unnecessary since we might as well
write the cost value directly into the table of the MSR's root node
(both costs and abstract states are represented by the same type).
N. distances:
 Distances computation could be made more finegrained. Which things
do we really need to recompute after shrinking? When do we need g
values, and when don't we? It might be a good idea to give the
shrink strategies and merge strategies a methods that let them tell
the overall algorithm whether they are interested in g values and/or
h values; e.g., only shrink_fh would be interested in g values;
merge_dfp is interested in h values; shrink_bisimulation is
interested in h values when using greedy bisimulation or when using
h for initialization (which at the moment we always use?).
 Should we make pruning irrelevant and/or unreachable states
configurable? Should it be a *separate* step that is controlled by
the main mergeandshrink loop? (Logically, it is a separate
transformation of the factored transition system. In practice, it
might be more efficient to couple it with other steps.)
 The vector<bool> of prunable states should probably be accessed the
same way as the g and h values, rather than using a separate
interface as it is done currently (g and h are stored in the
Distance object and requested individually; prunability is returned
as a complete vector).
O. FTSFactory
 We currently have a twostage initialization for the atomic
transition systems. First, they are created in an incomplete state,
and then the factory takes over the rest of the initialization. We
should have a constructor that generates them in one shot. 
20151126 13:27:56  silvan  set  messages:
+ msg4836 
20151126 13:22:55  silvan  set  summary: Open action items:
A. issue415: better memory management
B. Continue splitting TransitionSystem into several parts. (issue561 is now merged.)
C. TransitionSystem::compute_locally_equivalent_labels(): make computation
faster through sorting transitions (O(n log n)) or hashing (O(n)). Sorting is
probably better, because we do not need to consider all transitions in the best
case. [This doesn't seem to be a huuuuuge bottleneck, though. According to
experiments (not on the tracker), it can be up to 10% of mergeandshrink
construction time in some configs.]
D. Add a hybrid bisimulation/greedy bisimulation strategy, inspired from the
code used for the IJCAI 2011 paper. See also issue431.
E. Add a max_time parameter similar as in iPDB.
F. Consider adding a max_transitions or similar parameter (see msg4485).
G. Consider performing exact label reduction in some cases where the labels have
different cost.
H. Introduce a namespace for mergeandshrink.
I. Reconsider default values for shrinking strategy limits (msg4429, msg4430)?
J. Atomic transition system construction could be made faster w.r.t. irrelevant
operators (msg4462, item 1).
K. Atomic transition system construction could be made smarter w.r.t. multiple
conditional effects on the same variable. This would require dedicated domains
to test impact and correctness (msg4462, item 2). 
20151113 16:36:46  silvan  set  messages:
+ msg4790 
20151112 09:26:35  silvan  set  messages:
+ msg4779 
20150812 14:03:16  silvan  set  messages:
+ msg4577 
20150728 17:56:42  silvan  set  messages:
+ msg4522 
20150728 15:05:06  malte  set  messages:
+ msg4517 
20150728 15:04:05  malte  set  messages:
+ msg4516 
20150727 11:53:50  malte  set  messages:
+ msg4485 
20150727 11:45:19  silvan  create  
