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stockfish
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Move draw by material check 

It is more natural to test this case among
others material distributions.

No functional change.
sf_dd_base
Marco Costalba 2013-09-08 05:49:04 -07:00
parent 0515ad0fb0
commit 490f67a3f8
3 changed files with 17 additions and 13 deletions
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2
src/endgame.h
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@ -43,7 +43,7 @@ enum EndgameType {
KQKP, // KQ vs KP
KQKR, // KQ vs KR
KBBKN, // KBB vs KN
KmmKm, // K and two minors vs K and one or two minors
KmmKm, // K and one or two minors vs K and zero or one minor
// Scaling functions

15
src/material.cpp
View File

@ -173,10 +173,18 @@ Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
return e;
}
// Draw by insufficient material (trivial draws like KK, KBK and KNK)
if ( !pos.pieces(PAWN)
&& pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) <= BishopValueMg)
{
e->evaluationFunction = &EvaluateKmmKm[pos.side_to_move()];
return e;
}
// Minor piece endgame with at least one minor piece per side and
// no pawns. Note that the case KmmK is already handled by KXK.
if (!pos.pieces(PAWN) && !pos.pieces(ROOK) && !pos.pieces(QUEEN))
{
// Minor piece endgame with at least one minor piece per side and
// no pawns. Note that the case KmmK is already handled by KXK.
assert((pos.pieces(WHITE, KNIGHT) | pos.pieces(WHITE, BISHOP)));
assert((pos.pieces(BLACK, KNIGHT) | pos.pieces(BLACK, BISHOP)));
@ -240,8 +248,7 @@ Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
}
}
// No pawns makes it difficult to win, even with a material advantage. This
// catches some trivial draws like KK, KBK and KNK
// No pawns makes it difficult to win, even with a material advantage
if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
{
e->factor[WHITE] = (uint8_t)

13
src/position.cpp
View File

@ -1223,6 +1223,7 @@ Key Position::compute_material_key() const {
/// game and the endgame. These functions are used to initialize the incremental
/// scores when a new position is set up, and to verify that the scores are correctly
/// updated by do_move and undo_move when the program is running in debug mode.
Score Position::compute_psq_score() const {
Score score = SCORE_ZERO;
@ -1254,15 +1255,11 @@ Value Position::compute_non_pawn_material(Color c) const {
}
/// Position::is_draw() tests whether the position is drawn by material,
/// repetition, or the 50 moves rule. It does not detect stalemates, this
/// must be done by the search.
bool Position::is_draw() const {
/// Position::is_draw() tests whether the position is drawn by repetition
/// or the 50 moves rule. It does not detect stalemates, this must be done
/// by the search.
// Draw by material?
if ( !pieces(PAWN)
&& (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg))
return true;
bool Position::is_draw() const {
// Draw by the 50 moves rule?
if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))