Issue454

Title get rid of negated axiom rules in translator
Priority bug Status chatting
Superseder Nosy List malte, patrik
Assigned To Keywords translator
Optional summary
Check for references to "issue454" in the code, specifically axiom_rules.py and
sas_tasks.py. (Best look for references to issue454 in the whole codebase.)

Created on 2014-08-17.11:33:53 by malte, last changed by malte.

Summary
Check for references to "issue454" in the code, specifically axiom_rules.py and
sas_tasks.py. (Best look for references to issue454 in the whole codebase.)
Messages
msg8045 (view) Author: malte Date: 2018-11-04.04:57:38
BTW, I'm no longer convinced that changing this would only affect a few parts of
the code. It looks like at least most of our relaxation heuristics (h^FF, h^add,
h^max) make use of the axioms provided by the code, and ripping out the negated
axiom versions can have a strong negative impact on them.

I don't mean this as an excuse to leave this issue unfixed, of course. But it
does mean we need to tread a bit carefully. In particular, we should make sure
not to ruin performance in cases without cyclic dependencies, which includes all
cases where derived variables are currently artificially introduced by the
translator.
msg8044 (view) Author: malte Date: 2018-11-04.04:54:06
Made the summary more comprehensive.
msg8043 (view) Author: malte Date: 2018-11-04.04:28:20
I'm reclassifying this as a bug because the negated axiom rules mean that we can
currently have axiom rules with heads (v=0) and (v=1) for the same variable. (At
least I think that this can happen.)

This is not necessarily a problem due to the way the axioms are actually
constructed, but it does not agree with how we specified the layering condition
in the AIJ paper on the translator and elsewhere. So at the very least, we
should make the semantics and the behaviour of the translator clear.

One reasonable place where this could be documented (in addition to the code
itself) is http://www.fast-downward.org/TranslatorOutputFormat, in particular
sections "Variables section" and "Axiom section" and section "Evaluation axioms"
at the end.
msg8041 (view) Author: malte Date: 2018-11-04.04:10:22
The proposed fix for issue862 interacts with this issue.

I've added code comments to axiom_rules.py which explain the interaction. All
relevant comments mention the keyword "issue454", so searching for this keyword
in axiom_rules.py while working on this issue should be enough to find all of
them. I've added a reminder of this to the summary.
msg4289 (view) Author: malte Date: 2015-06-29.23:01:51
Note to self: when fixing this, search the code (in particular the translator)
for references to issue454. The work-in-progress code for issue533 has a code
comment related to this issue.
msg3320 (view) Author: malte Date: 2014-08-17.11:33:53
We currently generate "negated forms" of axiom rules in certain cases. This can
be very expensive, is only used in few contexts, and is apparently currently
buggy (see issue453).

This issue is about getting rid of these negated-form axioms. The most difficult
part in this is probably detecting all the places where they are implicitly used
(e.g. in relevance analysis?). We should also evaluate the performance impact on
planner configurations that make use of these negated axiom rules (such as the
CG heuristic and possibly some of the landmark generators) and possibly
reintroduce them locally for planner configurations that use them.
History
Date User Action Args
2018-11-04 04:57:38maltesetmessages: + msg8045
2018-11-04 04:54:06maltesetmessages: + msg8044
summary: Check for references to "issue454" in the code, specifically axiom_rules.py. -> Check for references to "issue454" in the code, specifically axiom_rules.py and sas_tasks.py. (Best look for references to issue454 in the whole codebase.)
2018-11-04 04:28:20maltesetpriority: wish -> bug
messages: + msg8043
2018-11-04 04:10:22maltesetmessages: + msg8041
summary: Check for references to "issue454" in the code, specifically axiom_rules.py.
2015-06-29 23:01:51maltesetmessages: + msg4289
2014-10-04 19:50:27maltesetkeyword: + translator
2014-08-18 04:59:08patriksetnosy: + patrik
2014-08-17 11:33:53maltecreate