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Document asymmetric SEE pruning trick

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Here are the tests:

sprt @ 60+0.05
ELO: 3.53 +-2.8 (95%) LOS: 99.3%
Total: 18794 W: 3098 L: 2907 D: 12789

16000 @ 60+0.05
ELO: 1.39 +-3.1 (95%) LOS: 81.0%
Total: 16000 W: 2689 L: 2625 D: 10686

16000 @ 15+0.05
ELO: 2.82 +-3.3 (95%) LOS: 95.1%
Total: 16000 W: 3148 L: 3018 D: 9834

No functional change

Signature: 4969307
This commit is contained in:
Joona Kiiski
2013-04-09 09:20:10 +01:00
committed by Marco Costalba
parent c2902112e5
commit d23454854e
3 changed files with 11 additions and 3 deletions
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9
src/position.cpp
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@@ -1151,6 +1151,11 @@ int Position::see(Move m) const {
return do_see<false>(m, 0); return do_see<false>(m, 0);
} }
/// Position::see_asymm() takes tempi into account.
/// If the side who initiated the capturing sequence does the last capture,
/// he loses a tempo. In this case if the result is below asymmThreshold
/// the capturing sequence is considered bad.
int Position::see_asymm(Move m, int asymmThreshold) const int Position::see_asymm(Move m, int asymmThreshold) const
{ {
return do_see<true>(m, asymmThreshold); return do_see<true>(m, asymmThreshold);
@@ -1234,7 +1239,9 @@ int Position::do_see(Move m, int asymmThreshold) const {
} while (stmAttackers); } while (stmAttackers);
// FIXME: Document // If we are doing asymmetric SEE evaluation and the same side does the first
// and the last capture, he loses a tempo and gain must be at least worth "asymmThreshold".
// If not, we replace the score with a very low value, before negamaxing.
if (Asymmetric) if (Asymmetric)
{ {
for (int i = 0; i < slIndex ; i += 2) for (int i = 0; i < slIndex ; i += 2)

2
src/position.h
View File

@@ -161,7 +161,6 @@ public:
int see(Move m) const; int see(Move m) const;
int see_sign(Move m) const; int see_sign(Move m) const;
int see_asymm(Move m, int asymmThreshold) const; int see_asymm(Move m, int asymmThreshold) const;
template <bool Asymmetric> int do_see(Move m, int asymmThreshold) const; //FIXME: private!!
// Accessing hash keys // Accessing hash keys
Key key() const; Key key() const;
@@ -195,6 +194,7 @@ private:
// Helper functions // Helper functions
void do_castle(Square kfrom, Square kto, Square rfrom, Square rto); void do_castle(Square kfrom, Square kto, Square rfrom, Square rto);
template<bool Asymmetric> int do_see(Move m, int asymmThreshold) const;
template<bool FindPinned> Bitboard hidden_checkers() const; template<bool FindPinned> Bitboard hidden_checkers() const;
// Computing hash keys from scratch (for initialization and debugging) // Computing hash keys from scratch (for initialization and debugging)

3
src/search.cpp
View File

@@ -1225,7 +1225,8 @@ split_point_start: // At split points actual search starts from here
continue; continue;
} }
// Prune moves with negative or equal SEE // Prune moves with negative or equal SEE.
// Also prune moves with positive SEE where capturing loses a tempo and SEE < beta - futilityBase.
if ( futilityBase < beta if ( futilityBase < beta
&& depth < DEPTH_ZERO && depth < DEPTH_ZERO
&& pos.see_asymm(move, beta - futilityBase) <= 0) && pos.see_asymm(move, beta - futilityBase) <= 0)