- moveCount = ++sp->moveCount;
- lock_release(&(sp->lock));
-
- assert(move_is_ok(move));
-
- moveIsCheck = pos.move_is_check(move, ci);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- // Step 11. Decide the new search depth
- ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
- newDepth = sp->depth - OnePly + ext;
-
- // Update current move
- ss[sp->ply].currentMove = move;
-
- // Step 12. Futility pruning (is omitted in PV nodes)
- if ( !PvNode
- && !isCheck
- && !dangerous
- && !captureOrPromotion
- && !move_is_castle(move))
- {
- // Move count based pruning
- if ( moveCount >= futility_move_count(sp->depth)
- && ok_to_prune(pos, move, ss[sp->ply].threatMove)
- && sp->bestValue > value_mated_in(PLY_MAX))
- {
- lock_grab(&(sp->lock));
- continue;
- }
-
- // Value based pruning
- Depth predictedDepth = newDepth - reduction<NonPV>(sp->depth, moveCount);
- futilityValueScaled = ss[sp->ply].eval + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_on(move_from(move)), move_to(move));
-
- if (futilityValueScaled < sp->beta)
- {
- lock_grab(&(sp->lock));
-
- if (futilityValueScaled > sp->bestValue)
- sp->bestValue = futilityValueScaled;
- continue;
- }
- }
-
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Step 14. Reduced search
- // if the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
-
- if ( !dangerous
- && !captureOrPromotion
- && !move_is_castle(move)
- && !move_is_killer(move, ss[sp->ply]))
- {
- ss[sp->ply].reduction = reduction<PvNode>(sp->depth, moveCount);
- if (ss[sp->ply].reduction)
- {
- Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss, -(localAlpha+1), -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
- doFullDepthSearch = (value > localAlpha);
- }
- }
-
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- ss[sp->ply].reduction = Depth(0);
- Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1, true, threadID);
-
- if (PvNode && value > localAlpha && value < sp->beta)
- value = -search<PV>(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, false, threadID);
- }
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- // Step 17. Check for new best move
- lock_grab(&(sp->lock));
-
- if (value > sp->bestValue && !TM.thread_should_stop(threadID))
- {
- sp->bestValue = value;
-
- if (sp->bestValue > sp->alpha)
- {
- if (!PvNode || value >= sp->beta)
- sp->stopRequest = true;
-
- if (PvNode && value < sp->beta) // This guarantees that always: sp->alpha < sp->beta
- sp->alpha = value;