// right to castle.
const Value TrappedRookPenalty = Value(180);
+ // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
+ // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
+ // happen in Chess960 games.
+ const Score TrappedBishopA1H1Penalty = make_score(100, 100);
+
// The SpaceMask[Color] contains the area of the board which is considered
// by the space evaluation. In the middle game, each side is given a bonus
// based on how many squares inside this area are safe and available for
template<Color Us>
Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
+ template<bool HasPopCnt>
+ Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
+
inline Score apply_weight(Score v, Score weight);
Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf);
Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
bonus += evaluate_passed_pawns<WHITE>(pos, ei)
- evaluate_passed_pawns<BLACK>(pos, ei);
+ // If one side has only a king, check whether exists any unstoppable passed pawn
+ if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
+ bonus += evaluate_unstoppable_pawns<HasPopCnt>(pos, ei);
+
// Evaluate space for both sides, only in middle-game.
if (mi->space_weight())
{
/// read_weights() reads evaluation weights from the corresponding UCI parameters
-void read_weights(Color us) {
+void read_evaluation_uci_options(Color us) {
// King safety is asymmetrical. Our king danger level is weighted by
// "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
}
+ // Special extra evaluation for bishops
+ if (Piece == BISHOP && pos.is_chess960())
+ {
+ // An important Chess960 pattern: A cornered bishop blocked by
+ // a friendly pawn diagonally in front of it is a very serious
+ // problem, especially when that pawn is also blocked.
+ if (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1))
+ {
+ SquareDelta d = pawn_push(Us)
+ + (square_file(s) == FILE_A ? DELTA_E : DELTA_W);
+ if (pos.piece_on(s + d) == piece_of_color_and_type(Us, PAWN))
+ {
+ if (!pos.square_is_empty(s + d + pawn_push(Us)))
+ bonus -= 2*TrappedBishopA1H1Penalty;
+ else if (pos.piece_on(s + 2*d) == piece_of_color_and_type(Us, PAWN))
+ bonus -= TrappedBishopA1H1Penalty;
+ else
+ bonus -= TrappedBishopA1H1Penalty / 2;
+ }
+ }
+ }
+
// Special extra evaluation for rooks
if (Piece == ROOK)
{
return apply_weight(bonus, Weights[PassedPawns]);
}
+ // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
+ template<bool HasPopCnt>
+ Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
+
+ const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
+
+ // Step 1. Hunt for unstoppable pawns. If we find at least one, record how many plies
+ // are required for promotion
+ int pliesToGo[2] = {256, 256};
+
+ for (Color c = WHITE; c <= BLACK; c++)
+ {
+ // Skip if other side has non-pawn pieces
+ if (pos.non_pawn_material(opposite_color(c)))
+ continue;
+
+ Bitboard b = ei.pi->passed_pawns(c);
+
+ while (b)
+ {
+ Square s = pop_1st_bit(&b);
+ Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
+
+ int mtg = RANK_8 - relative_rank(c, s) - int(relative_rank(c, s) == RANK_2);
+ int oppmtg = square_distance(pos.king_square(opposite_color(c)), queeningSquare) - int(c != pos.side_to_move());
+ bool pathDefended = ((ei.attackedBy[c][0] & squares_in_front_of(c, s)) == squares_in_front_of(c, s));
+
+ if (mtg >= oppmtg && !pathDefended)
+ continue;
+
+ int blockerCount = count_1s<Max15>(squares_in_front_of(c, s) & pos.occupied_squares());
+ mtg += blockerCount;
+
+ if (mtg >= oppmtg && !pathDefended)
+ continue;
+
+ int ptg = 2 * mtg - int(c == pos.side_to_move());
+
+ if (ptg < pliesToGo[c])
+ pliesToGo[c] = ptg;
+ }
+ }
+
+ // Step 2. If either side cannot promote at least three plies before the other side then
+ // situation becomes too complex and we give up. Otherwise we determine the possibly "winning side"
+ if (abs(pliesToGo[WHITE] - pliesToGo[BLACK]) < 3)
+ return make_score(0, 0);
+
+ Color winnerSide = (pliesToGo[WHITE] < pliesToGo[BLACK] ? WHITE : BLACK);
+ Color loserSide = opposite_color(winnerSide);
+
+ // Step 3. Can the losing side possibly create a new passed pawn and thus prevent the loss?
+ // We collect the potential candidates in potentialBB.
+ Bitboard pawnBB = pos.pieces(PAWN, loserSide);
+ Bitboard potentialBB = pawnBB;
+ const Bitboard passedBB = ei.pi->passed_pawns(loserSide);
+
+ while(pawnBB)
+ {
+ Square psq = pop_1st_bit(&pawnBB);
+
+ // Check direct advancement
+ int mtg = RANK_8 - relative_rank(loserSide, psq) - int(relative_rank(loserSide, psq) == RANK_2);
+ int ptg = 2 * mtg - int(loserSide == pos.side_to_move());
+
+ // Check if (without even considering any obstacles) we're too far away
+ if (pliesToGo[winnerSide] + 3 <= ptg)
+ {
+ clear_bit(&potentialBB, psq);
+ continue;
+ }
+
+ // If this is passed pawn, then it _may_ promote in time. We give up.
+ if (bit_is_set(passedBB, psq))
+ return make_score(0, 0);
+
+ // Doubled pawn is worthless
+ if (squares_in_front_of(loserSide, psq) & (pos.pieces(PAWN, loserSide)))
+ {
+ clear_bit(&potentialBB, psq);
+ continue;
+ }
+ }
+
+ // Step 4. Check new passed pawn creation through king capturing and sacrifises
+ pawnBB = potentialBB;
+
+ while(pawnBB)
+ {
+ Square psq = pop_1st_bit(&pawnBB);
+
+ int mtg = RANK_8 - relative_rank(loserSide, psq) - int(relative_rank(loserSide, psq) == RANK_2);
+ int ptg = 2 * mtg - int(loserSide == pos.side_to_move());
+
+ // Generate list of obstacles
+ Bitboard obsBB = passed_pawn_mask(loserSide, psq) & pos.pieces(PAWN, winnerSide);
+ const bool pawnIsOpposed = squares_in_front_of(loserSide, psq) & obsBB;
+ assert(obsBB);
+
+ // How many plies does it take to remove all the obstacles?
+ int sacptg = 0;
+ int realObsCount = 0;
+ int minKingDist = 256;
+
+ while(obsBB)
+ {
+ Square obSq = pop_1st_bit(&obsBB);
+ int minMoves = 256;
+
+ // Check pawns that can give support to overcome obstacle (Eg. wp: a4,b4 bp: b2. b4 is giving support)
+ if (!pawnIsOpposed && square_file(psq) != square_file(obSq))
+ {
+ Bitboard supBB = in_front_bb(winnerSide, Square(obSq + (winnerSide == WHITE ? 8 : -8)))
+ & neighboring_files_bb(psq) & potentialBB;
+
+ while(supBB) // This while-loop could be replaced with supSq = LSB/MSB(supBB) (depending on color)
+ {
+ Square supSq = pop_1st_bit(&supBB);
+ int dist = square_distance(obSq, supSq);
+ minMoves = Min(minMoves, dist - 2);
+ }
+
+ }
+
+ // Check pawns that can be sacrifised
+ Bitboard sacBB = passed_pawn_mask(winnerSide, obSq) & neighboring_files_bb(obSq) & potentialBB & ~(1ULL << psq);
+
+ while(sacBB) // This while-loop could be replaced with sacSq = LSB/MSB(sacBB) (depending on color)
+ {
+ Square sacSq = pop_1st_bit(&sacBB);
+ int dist = square_distance(obSq, sacSq);
+ minMoves = Min(minMoves, dist - 2);
+ }
+
+ // If obstacle can be destroyed with immediate pawn sacrifise, it's not real obstacle
+ if (minMoves <= 0)
+ continue;
+
+ // Pawn sac calculations
+ sacptg += minMoves * 2;
+
+ // King capture calc
+ realObsCount++;
+ int kingDist = square_distance(pos.king_square(loserSide), obSq);
+ minKingDist = Min(minKingDist, kingDist);
+ }
+
+ // Check if pawn sac plan _may_ save the day
+ if (pliesToGo[winnerSide] + 3 > ptg + sacptg)
+ return make_score(0, 0);
+
+ // Check if king capture plan _may_ save the day (contains some false positives)
+ int kingptg = (minKingDist + realObsCount) * 2;
+ if (pliesToGo[winnerSide] + 3 > ptg + kingptg)
+ return make_score(0, 0);
+ }
+
+ // Step 5. Assign bonus
+ const int Sign[2] = {1, -1};
+ return Sign[winnerSide] * make_score(0, (Value) 0x500 - 0x20 * pliesToGo[winnerSide]);
+ }
+
// evaluate_space() computes the space evaluation for a given side. The
// space evaluation is a simple bonus based on the number of safe squares
projects / stockfish / blobdiff