- staticValue = -VALUE_INFINITE;
- else if (tte && (tte->type() & VALUE_TYPE_EVAL))
- staticValue = value_from_tt(tte->value(), ply);
- else
- staticValue = evaluate(pos, ei, threadID);
-
- if (!isCheck)
- {
- ss[ply].eval = staticValue;
- update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
- }
-
- // Initialize "stand pat score", and return it immediately if it is
- // at least beta.
- bestValue = staticValue;
-
- if (bestValue >= beta)
- {
- // Store the score to avoid a future costly evaluation() call
- if (!isCheck && !tte && ei.kingDanger[pos.side_to_move()] == 0)
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EV_LO, Depth(-127*OnePly), MOVE_NONE);
-
- return bestValue;
- }
-
- if (bestValue > alpha)
- alpha = bestValue;
-
- // If we are near beta then try to get a cutoff pushing checks a bit further
- bool deepChecks = (depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8);
-
- // Initialize a MovePicker object for the current position, and prepare
- // to search the moves. Because the depth is <= 0 here, only captures,
- // queen promotions and checks (only if depth == 0 or depth == -OnePly
- // and we are near beta) will be generated.
- MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H);
- CheckInfo ci(pos);
- enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
- futilityBase = staticValue + FutilityMarginQS + ei.kingDanger[pos.side_to_move()];
-
- // Loop through the moves until no moves remain or a beta cutoff occurs
- while ( alpha < beta
- && (move = mp.get_next_move()) != MOVE_NONE)
- {
- assert(move_is_ok(move));
-
- moveIsCheck = pos.move_is_check(move, ci);
-
- // Update current move
- moveCount++;
- ss[ply].currentMove = move;
-
- // Futility pruning
- if ( enoughMaterial
- && !isCheck
- && !pvNode
- && !moveIsCheck
- && move != ttMove
- && !move_is_promotion(move)
- && !pos.move_is_passed_pawn_push(move))
- {
- futilityValue = futilityBase
- + pos.endgame_value_of_piece_on(move_to(move))
- + (move_is_ep(move) ? PawnValueEndgame : Value(0));
-
- if (futilityValue < alpha)
- {
- if (futilityValue > bestValue)
- bestValue = futilityValue;
- continue;
- }
- }
-
- // Detect blocking evasions that are candidate to be pruned
- evasionPrunable = isCheck
- && bestValue > value_mated_in(PLY_MAX)
- && !pos.move_is_capture(move)
- && pos.type_of_piece_on(move_from(move)) != KING
- && !pos.can_castle(pos.side_to_move());
-
- // Don't search moves with negative SEE values
- if ( (!isCheck || evasionPrunable)
- && !pvNode
- && move != ttMove
- && !move_is_promotion(move)
- && pos.see_sign(move) < 0)
- continue;
-
- // Make and search the move
- pos.do_move(move, st, ci, moveIsCheck);
- value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- // New best move?
- if (value > bestValue)
- {
- bestValue = value;
- if (value > alpha)
- {
- alpha = value;
- update_pv(ss, ply);
- }
- }
- }
-
- // All legal moves have been searched. A special case: If we're in check
- // and no legal moves were found, it is checkmate.
- if (!moveCount && isCheck) // Mate!
- return value_mated_in(ply);
-
- // Update transposition table
- Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
- if (bestValue <= oldAlpha)
- {
- // If bestValue isn't changed it means it is still the static evaluation
- // of the node, so keep this info to avoid a future evaluation() call.
- ValueType type = (bestValue == staticValue && !ei.kingDanger[pos.side_to_move()] ? VALUE_TYPE_EV_UP : VALUE_TYPE_UPPER);
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), type, d, MOVE_NONE);
- }
- else if (bestValue >= beta)