HCha/Stockfish
1
0
Fork 0
mirror of https://github.com/HChaZZY/Stockfish.git synced 2025-12-24 19:16:49 +08:00
Code Issues Packages Projects Releases Wiki Activity

Introduce scale factor in pawn evaluation

Browse Source 
The idea is to reduce the score if we have many
pawns opposing an enemy pawn so that the draw
possibility increases.

Just introduced the logic, but no functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2010-04-18 10:25:59 +01:00
parent c23cd4d90a
commit 6b7efa0cd1
5 changed files with 33 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
src/pawns.cpp
View File

@@ -70,6 +70,13 @@ namespace {
S(34,68), S(83,166), S(0, 0), S( 0, 0)
};
// UnpairedPawnsTable[] gives a score according to the number
// of panws that do not have an enemy pawn in front of them.
const int UnpairedPawnsTable[8] = {
SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL,
SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL
};
// Pawn storm tables for positions with opposite castling
const int QStormTable[64] = {
0, 0, 0, 0, 0, 0, 0, 0,
@@ -187,6 +194,7 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
int bonus;
Score value = make_score(0, 0);
const Square* ptr = pos.piece_list_begin(Us, PAWN);
int unpairedPawnsNum = pos.piece_count(Us, PAWN);
// Initialize pawn storm scores by giving bonuses for open files
for (f = FILE_A; f <= FILE_H; f++)
@@ -211,6 +219,10 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
doubled = ourPawns & squares_behind(Us, s);
opposed = theirPawns & squares_in_front_of(Us, s);
// Decrease number of unpaired pawns
if (opposed)
unpairedPawnsNum--;
// We calculate kingside and queenside pawn storm
// scores for both colors. These are used when evaluating
// middle game positions with opposite side castling.
@@ -337,6 +349,9 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
value += CandidateBonus[relative_rank(Us, s)];
}
// Calculate a scale factor to be used to evaluate if position is drawish
pi->factor[Us] = UnpairedPawnsTable[unpairedPawnsNum];
return value;
}