// evaluate_passed_pawns() evaluates the passed pawns for both sides.
void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
+
bool hasUnstoppable[2] = {false, false};
int movesToGo[2] = {100, 100};
- for(Color us = WHITE; us <= BLACK; us++) {
- Color them = opposite_color(us);
- Square ourKingSq = pos.king_square(us);
- Square theirKingSq = pos.king_square(them);
- Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
+ for (Color us = WHITE; us <= BLACK; us++)
+ {
+ Color them = opposite_color(us);
+ Square ourKingSq = pos.king_square(us);
+ Square theirKingSq = pos.king_square(them);
+ Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
- while(b) {
- Square s = pop_1st_bit(&b);
- assert(pos.piece_on(s) == pawn_of_color(us));
- assert(pos.pawn_is_passed(us, s));
-
- int r = int(relative_rank(us, s) - RANK_2);
- int tr = Max(0, r * (r-1));
- Square blockSq = s + pawn_push(us);
-
- // Base bonus based on rank:
- Value mbonus = Value(20 * tr);
- Value ebonus = Value(10 + r * r * 10);
-
- // Adjust bonus based on king proximity:
- ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
- ebonus -=
- Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
- ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
-
- // If the pawn is free to advance, increase bonus:
- if(pos.square_is_empty(blockSq)) {
-
- b2 = squares_in_front_of(us, s);
- b3 = b2 & ei.attacked_by(them);
- b4 = b2 & ei.attacked_by(us);
-
- // If there is an enemy rook or queen attacking the pawn from behind,
- // add all X-ray attacks by the rook or queen.
- if(bit_is_set(ei.attacked_by(them,ROOK)|ei.attacked_by(them,QUEEN),s)
- && squares_behind(us, s) & pos.rooks_and_queens(them))
- b3 = b2;
-
- if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
- // There are no enemy pieces in the pawn's path! Are any of the
- // squares in the pawn's path attacked by the enemy?
- if(b3 == EmptyBoardBB)
- // No enemy attacks, huge bonus!
- ebonus += Value(tr * ((b2 == b4)? 17 : 15));
- else
- // OK, there are enemy attacks. Are those squares which are
- // attacked by the enemy also attacked by us? If yes, big bonus
- // (but smaller than when there are no enemy attacks), if no,
- // somewhat smaller bonus.
- ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
- }
- else {
- // There are some enemy pieces in the pawn's path. While this is
- // sad, we still assign a moderate bonus if all squares in the path
- // which are either occupied by or attacked by enemy pieces are
- // also attacked by us.
- if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
- ebonus += Value(tr * 6);
- }
- // At last, add a small bonus when there are no *friendly* pieces
- // in the pawn's path:
- if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
- ebonus += Value(tr);
- }
+ while (b)
+ {
+ Square s = pop_1st_bit(&b);
+
+ assert(pos.piece_on(s) == pawn_of_color(us));
+ assert(pos.pawn_is_passed(us, s));
+
+ int r = int(relative_rank(us, s) - RANK_2);
+ int tr = Max(0, r * (r - 1));
+ Square blockSq = s + pawn_push(us);
+
+ // Base bonus based on rank
+ Value mbonus = Value(20 * tr);
+ Value ebonus = Value(10 + r * r * 10);
+
+ // Adjust bonus based on king proximity
+ ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
+ ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
+ ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
+
+ // If the pawn is free to advance, increase bonus
+ if (pos.square_is_empty(blockSq))
+ {
+ b2 = squares_in_front_of(us, s);
+ b3 = b2 & ei.attacked_by(them);
+ b4 = b2 & ei.attacked_by(us);
+
+ // If there is an enemy rook or queen attacking the pawn from behind,
+ // add all X-ray attacks by the rook or queen.
+ if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
+ && (squares_behind(us, s) & pos.rooks_and_queens(them)))
+ b3 = b2;
+
+ if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
+ {
+ // There are no enemy pieces in the pawn's path! Are any of the
+ // squares in the pawn's path attacked by the enemy?
+ if (b3 == EmptyBoardBB)
+ // No enemy attacks, huge bonus!
+ ebonus += Value(tr * (b2 == b4 ? 17 : 15));
+ else
+ // OK, there are enemy attacks. Are those squares which are
+ // attacked by the enemy also attacked by us? If yes, big bonus
+ // (but smaller than when there are no enemy attacks), if no,
+ // somewhat smaller bonus.
+ ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
+ }
+ else
+ {
+ // There are some enemy pieces in the pawn's path. While this is
+ // sad, we still assign a moderate bonus if all squares in the path
+ // which are either occupied by or attacked by enemy pieces are
+ // also attacked by us.
+ if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
+ ebonus += Value(tr * 6);
+ }
+ // At last, add a small bonus when there are no *friendly* pieces
+ // in the pawn's path.
+ if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
+ ebonus += Value(tr);
+ }
+
+ // If the pawn is supported by a friendly pawn, increase bonus
+ b2 = pos.pawns(us) & neighboring_files_bb(s);
+ if (b2 & rank_bb(s))
+ ebonus += Value(r * 20);
+ else if (pos.pawn_attacks(them, s) & b2)
+ ebonus += Value(r * 12);
+
+ // If the other side has only a king, check whether the pawn is
+ // unstoppable
+ if (pos.non_pawn_material(them) == Value(0))
+ {
+ Square qsq;
+ int d;
+
+ qsq = relative_square(us, make_square(square_file(s), RANK_8));
+ d = square_distance(s, qsq)
+ - square_distance(theirKingSq, qsq)
+ + (us != pos.side_to_move());
- // If the pawn is supported by a friendly pawn, increase bonus.
- b2 = pos.pawns(us) & neighboring_files_bb(s);
- if(b2 & rank_bb(s))
- ebonus += Value(r * 20);
- else if(pos.pawn_attacks(them, s) & b2)
- ebonus += Value(r * 12);
-
- // If the other side has only a king, check whether the pawn is
- // unstoppable:
- if(pos.non_pawn_material(them) == Value(0)) {
- Square qsq;
- int d;
-
- qsq = relative_square(us, make_square(square_file(s), RANK_8));
- d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
- + ((us == pos.side_to_move())? 0 : 1);
-
- if(d < 0) {
- int mtg = RANK_8 - relative_rank(us, s);
- int blockerCount =
- count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
- mtg += blockerCount;
- d += blockerCount;
- if(d < 0) {
- hasUnstoppable[us] = true;
- movesToGo[us] = Min(movesToGo[us], mtg);
+ if (d < 0)
+ {
+ int mtg = RANK_8 - relative_rank(us, s);
+ int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
+ mtg += blockerCount;
+ d += blockerCount;
+ if (d < 0)
+ {
+ hasUnstoppable[us] = true;
+ movesToGo[us] = Min(movesToGo[us], mtg);
+ }
+ }
+ }
+ // Rook pawns are a special case: They are sometimes worse, and
+ // sometimes better than other passed pawns. It is difficult to find
+ // good rules for determining whether they are good or bad. For now,
+ // we try the following: Increase the value for rook pawns if the
+ // other side has no pieces apart from a knight, and decrease the
+ // value if the other side has a rook or queen.
+ if (square_file(s) == FILE_A || square_file(s) == FILE_H)
+ {
+ if( pos.non_pawn_material(them) == KnightValueMidgame // FIXME should be <= ???
+ && pos.piece_count(them, KNIGHT) == 1)
+ ebonus += ebonus / 4;
+ else if(pos.rooks_and_queens(them))
+ ebonus -= ebonus / 4;
}
- }
- }
- // Rook pawns are a special case: They are sometimes worse, and
- // sometimes better than other passed pawns. It is difficult to find
- // good rules for determining whether they are good or bad. For now,
- // we try the following: Increase the value for rook pawns if the
- // other side has no pieces apart from a knight, and decrease the
- // value if the other side has a rook or queen.
- if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
- if(pos.non_pawn_material(them) == KnightValueMidgame
- && pos.piece_count(them, KNIGHT) == 1)
- ebonus += ebonus / 4;
- else if(pos.rooks_and_queens(them))
- ebonus -= ebonus / 4;
- }
- // Add the scores for this pawn to the middle game and endgame eval.
- ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
- ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
- }
+ // Add the scores for this pawn to the middle game and endgame eval.
+ ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
+ ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
+ }
}
// Does either side have an unstoppable passed pawn?
- if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
- ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
- else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
- ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
- else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
- // Both sides have unstoppable pawns! Try to find out who queens
- // first. We begin by transforming 'movesToGo' to the number of
- // plies until the pawn queens for both sides:
- movesToGo[WHITE] *= 2;
- movesToGo[BLACK] *= 2;
- movesToGo[pos.side_to_move()]--;
-
- // If one side queens at least three plies before the other, that
- // side wins:
- if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
- ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
- else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
- ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
-
- // We could also add some rules about the situation when one side
- // queens exactly one ply before the other: Does the first queen
- // check the opponent's king, or attack the opponent's queening square?
- // This is slightly tricky to get right, because it is possible that
- // the opponent's king has moved somewhere before the first pawn queens.
+ if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
+ ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
+ else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
+ ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
+ else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
+ {
+ // Both sides have unstoppable pawns! Try to find out who queens
+ // first. We begin by transforming 'movesToGo' to the number of
+ // plies until the pawn queens for both sides.
+ movesToGo[WHITE] *= 2;
+ movesToGo[BLACK] *= 2;
+ movesToGo[pos.side_to_move()]--;
+
+ // If one side queens at least three plies before the other, that
+ // side wins.
+ if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
+ ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
+ else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
+ ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
+
+ // We could also add some rules about the situation when one side
+ // queens exactly one ply before the other: Does the first queen
+ // check the opponent's king, or attack the opponent's queening square?
+ // This is slightly tricky to get right, because it is possible that
+ // the opponent's king has moved somewhere before the first pawn queens.
}
}
projects / stockfish / commitdiff