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Merge new pawn storm evaluation

More accuracy in pawn storm evaluation
directly from iPhone Glaurung.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
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commit 320630ca1ab2792c31604ceca3e052159699b9b8 1 parent ef8acdc
@mcostalba authored
Showing with 63 additions and 52 deletions.
  1. +63 −52 src/pawns.cpp
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115 src/pawns.cpp
@@ -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).
-
- // 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;
+ // (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 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] += 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->ksStormValue[us] += KBonus;
- pi->qsStormValue[us] += QBonus;
+ 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
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