Author: Steven Edwards
Date: 09:44:38 03/17/04
Symbolic: Example outline of a search
Here's WAC.001:
[D] 2rr3k/pp3pp1/1nnqbN1p/3pN3/2pP4/2P3Q1/PPB4P/R4RK1 w - - 0 1
Symbolic gets the position from the stream interface, does a few validity
checks, creates the root of the move tree, probes the opening book and the
tablebases, checks for mate-in-1, etc. When none of the easy attempts work, it
then starts the real search.
The root position is submitted to the pattern matcher with the directive to run
all of the patterns in the bootstrap group and to associate the resulting
instances with the root node.
The matcher generates instances for all the matched bootstrap patterns including
the legal moves, hung pieces, pins, etc. The very last pattern it runs is the
Surveyor pattern. Surveyor takes a global look at all of the bootstrap
instances and decides which additional pattern groups to activate (i.e., make
eligible) for pattern matching. In the above position, Surveyor notices that an
attack on Black's king is a reasonable possibility, so it activates the KingHunt
pattern Group.
The KingHunt group includes the AlmostMate pattern:
(AlmostMate ((Move move1) (ManSq (man2 sq2)))
which matches the condition that move m1 would be a mate in one if it only
weren't for the presence of man man2 on square sq2. This pattern gets a match
producing the instance:
(AlmostMate (Move Ng6+) (ManSq (BlackPawn SqF7)))
The KingHunt group also includes the ThreatensMateInOne pattern:
(ThreatenMateInOne (Move move1))
which gets an instance:
(ThreatenMateInOne (Move Qg6))
This in turn triggers a match of a more general pattern, ForcedReply:
(ForcedReply (Move move1) (Move move2))
giving the instance:
(ForcedReply (Move Qg6) (Move fxg6))
When no more pattern matches occur, Symbolic then invokes its plan generator on
all the instances associated with the root node. After rummaging around with
the instances, it has tied together the above matches and produced a plan:
((Play Qg6)
(Replies
((fxg6) (TryToMate Ng6))
((Other (fxg6)) (TryToMate Qh7))))
Symbolic sends this plan to the plan verification process, and this expands a
handful of nodes. The plan is shown to be correct. Symbolic notes the selected
move, the PV, and the expectation. Seeing that nothing better can be had, it
records the results, sends them back via the stream interface, and exits.
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Last modified: Thu, 15 Apr 21 08:11:13 -0700
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