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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
};
// Pawn storm open file bonuses by file:
const int KStormOpenFileBonus[8] = {
45, 45, 30, 0, 0, 0, 0, 0
};
// Pawn storm open file bonuses by file
const int KStormOpenFileBonus[8] = { 45, 45, 30, 0, 0, 0, 0, 0 };
const int QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 30, 45, 30 };
const int QStormOpenFileBonus[8] = {
0, 0, 0, 0, 0, 30, 45, 30
};
// Pawn storm lever bonuses by file
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 theirPawns = pos.pawns(them);
Bitboard pawns = ourPawns;
int bonus;
// Initialize pawn storm scores by giving bonuses for open files
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);
doubled = pos.pawn_is_doubled(us, s);
// We calculate kingside and queenside pawn storm scores
// for both colors. These are used when evaluating middle
// game positions with opposite side castling.
// We calculate kingside and queenside pawn storm
// scores for both colors. These are used when evaluating
// middle game positions with opposite side castling.
//
// Each pawn is given a base score given by a piece square table
// (KStormTable[] or QStormTable[]). This score is increased if
// there are enemy pawns on adjacent files in front of the pawn.
// This is because we want to be able to open files against the
// enemy king, and to avoid blocking the pawn structure (e.g. white
// pawns on h6, g5, black pawns on h7, g6, f7).
// (KStormTable[] or QStormTable[]). Pawns which seem to have good
// chances of creating an open file by exchanging itself against an
// enemy pawn on an adjacent file gets an additional bonus.
// Kingside and queenside pawn storms
int KBonus = KStormTable[relative_square(us, s)];
int QBonus = QStormTable[relative_square(us, s)];
bool outPostFlag = (KBonus > 0 && (outpost_mask(us, s) & theirPawns));
bool passedFlag = (QBonus > 0 && (passed_pawn_mask(us, s) & theirPawns));
switch (f) {
case FILE_A:
QBonus += passedFlag * QBonus / 2;
break;
case FILE_B:
QBonus += passedFlag * (QBonus / 2 + QBonus / 4);
break;
case FILE_C:
QBonus += passedFlag * QBonus / 2;
break;
case FILE_F:
KBonus += outPostFlag * KBonus / 4;
break;
case FILE_G:
KBonus += outPostFlag * (KBonus / 2 + KBonus / 4);
break;
case FILE_H:
KBonus += outPostFlag * KBonus / 2;
break;
default:
break;
// Kingside pawn storms
bonus = KStormTable[relative_square(us, s)];
if (f >= FILE_F)
{
Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
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_H)
bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2);
else
bonus += 2*StormLeverBonus[f] - 4*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] - 2*square_distance(s, s2);
}
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
// the test a little by introducing an array of masks indexed by color