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Merge new pawn storm evaluation

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More accuracy in pawn storm evaluation
directly from iPhone Glaurung.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-03-22 13:55:08 +01:00
parent ef8acdc73b
commit 320630ca1a
1 changed files with 62 additions and 51 deletions
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113
src/pawns.cpp
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@ -120,14 +120,12 @@ namespace {
0, 0, 0, 0, 0, 0, 0, 0 0, 0, 0, 0, 0, 0, 0, 0
}; };
// Pawn storm open file bonuses by file: // Pawn storm open file bonuses by file
const int KStormOpenFileBonus[8] = { const int KStormOpenFileBonus[8] = { 45, 45, 30, 0, 0, 0, 0, 0 };
45, 45, 30, 0, 0, 0, 0, 0 const int QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 30, 45, 30 };
};
const int QStormOpenFileBonus[8] = { // Pawn storm lever bonuses by file
0, 0, 0, 0, 0, 30, 45, 30 const int StormLeverBonus[8] = { 20, 20, 10, 0, 0, 10, 20, 20 };
};
} }
@ -200,6 +198,7 @@ PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) {
Bitboard ourPawns = pos.pawns(us); Bitboard ourPawns = pos.pawns(us);
Bitboard theirPawns = pos.pawns(them); Bitboard theirPawns = pos.pawns(them);
Bitboard pawns = ourPawns; Bitboard pawns = ourPawns;
int bonus;
// Initialize pawn storm scores by giving bonuses for open files // Initialize pawn storm scores by giving bonuses for open files
for (File f = FILE_A; f <= FILE_H; f++) for (File f = FILE_A; f <= FILE_H; f++)
@ -227,54 +226,66 @@ PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) {
isolated = pos.pawn_is_isolated(us, s); isolated = pos.pawn_is_isolated(us, s);
doubled = pos.pawn_is_doubled(us, s); doubled = pos.pawn_is_doubled(us, s);
// We calculate kingside and queenside pawn storm scores // We calculate kingside and queenside pawn storm
// for both colors. These are used when evaluating middle // scores for both colors. These are used when evaluating
// game positions with opposite side castling. // middle game positions with opposite side castling.
// //
// Each pawn is given a base score given by a piece square table // Each pawn is given a base score given by a piece square table
// (KStormTable[] or QStormTable[]). This score is increased if // (KStormTable[] or QStormTable[]). Pawns which seem to have good
// there are enemy pawns on adjacent files in front of the pawn. // chances of creating an open file by exchanging itself against an
// This is because we want to be able to open files against the // enemy pawn on an adjacent file gets an additional bonus.
// enemy king, and to avoid blocking the pawn structure (e.g. white
// pawns on h6, g5, black pawns on h7, g6, f7).
// Kingside and queenside pawn storms // Kingside pawn storms
int KBonus = KStormTable[relative_square(us, s)]; bonus = KStormTable[relative_square(us, s)];
int QBonus = QStormTable[relative_square(us, s)]; if (f >= FILE_F)
bool outPostFlag = (KBonus > 0 && (outpost_mask(us, s) & theirPawns)); {
bool passedFlag = (QBonus > 0 && (passed_pawn_mask(us, s) & theirPawns)); Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
while (b)
switch (f) { {
Square s2 = pop_1st_bit(&b);
case FILE_A: if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
QBonus += passedFlag * QBonus / 2; {
break; // The enemy pawn has no pawn beside itself, which makes it
// particularly vulnerable. Big bonus, especially against a
case FILE_B: // weakness on the rook file.
QBonus += passedFlag * (QBonus / 2 + QBonus / 4); if (square_file(s2) == FILE_H)
break; bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2);
else
case FILE_C: bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2);
QBonus += passedFlag * QBonus / 2; } else
break; // There is at least one enemy pawn beside the enemy pawn we look
// at, which means that the pawn has somewhat better chances of
case FILE_F: // defending itself by advancing. Smaller bonus.
KBonus += outPostFlag * KBonus / 4; bonus += StormLeverBonus[f] - 2*square_distance(s, s2);
break;
case FILE_G:
KBonus += outPostFlag * (KBonus / 2 + KBonus / 4);
break;
case FILE_H:
KBonus += outPostFlag * KBonus / 2;
break;
default:
break;
} }
pi->ksStormValue[us] += KBonus; }
pi->qsStormValue[us] += QBonus; pi->ksStormValue[us] += bonus;
// Queenside pawn storms
bonus = QStormTable[relative_square(us, s)];
if (f <= FILE_C)
{
Bitboard b = outpost_mask(us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
while (b)
{
Square s2 = pop_1st_bit(&b);
if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
{
// The enemy pawn has no pawn beside itself, which makes it
// particularly vulnerable. Big bonus, especially against a
// weakness on the rook file.
if (square_file(s2) == FILE_A)
bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2);
else
bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2);
} else
// There is at least one enemy pawn beside the enemy pawn we look
// at, which means that the pawn has somewhat better chances of
// defending itself by advancing. Smaller bonus.
bonus += StormLeverBonus[f] - 4*square_distance(s, s2);
}
}
pi->qsStormValue[us] += bonus;
// Member of a pawn chain (but not the backward one)? We could speed up // Member of a pawn chain (but not the backward one)? We could speed up
// the test a little by introducing an array of masks indexed by color // the test a little by introducing an array of masks indexed by color