From an email by Blai:
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Hi Malte,
I've been playing around with the planner. I am interested
in computing mutexes between atoms using the hm (m=2)
heuristic in hm_heuristic.cc.
Apparently, some information is lost when the SAS instance
is computed. For example, in prob01 from Gripper, the SAS
translation has the variables (from the file test.groups):
var0:
0: Atom carry(ball1, right)
1: Atom carry(ball2, right)
2: Atom carry(ball3, right)
3: Atom free(right)
4: Atom carry(ball4, right)
var1:
0: Atom carry(ball3, left)
1: Atom free(left)
2: Atom carry(ball2, left)
3: Atom carry(ball1, left)
4: Atom carry(ball4, left)
var2:
0: Atom at(ball4, rooma)
1: Atom at(ball4, roomb)
2: <none of those>
var3:
0: Atom at(ball3, rooma)
1: Atom at(ball3, roomb)
2: <none of those>
var4:
0: Atom at(ball1, rooma)
1: Atom at(ball1, roomb)
2: <none of those>
var5:
0: Atom at(ball2, rooma)
1: Atom at(ball2, roomb)
2: <none of those>
var6:
0: Atom at-robby(roomb)
1: Atom at-robby(rooma)
From these, I cannot infer that the atoms at(ball1,left)
and at(ball1,right) are in mutex relation. I tried to
recover this information using the h2 heuristic, but the
h2 value for this pair is less than infinite (10000 in the
implementation) and thus the pair is not detected as mutex.
Indeed, the h2 values for *all* pairs in this problem are
less than infinite.
So, does this make sense to you? Is there any other way
of getting the mutex information?
Thanks and cheers,
Blai
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