- 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 && pos.is_check()) // 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.futilityMargin[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)
- {
- move = ss[ply].pv[ply];
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move);
-
- // Update killers only for good checking moves
- if (!pos.move_is_capture_or_promotion(move))
- update_killers(move, ss[ply]);
- }
- else
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, d, ss[ply].pv[ply]);
-
- assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
-
- return bestValue;
- }
-
-
- // sp_search() is used to search from a split point. This function is called
- // by each thread working at the split point. It is similar to the normal
- // search() function, but simpler. Because we have already probed the hash
- // table, done a null move search, and searched the first move before
- // splitting, we don't have to repeat all this work in sp_search(). We
- // also don't need to store anything to the hash table here: This is taken
- // care of after we return from the split point.
-
- void sp_search(SplitPoint* sp, int threadID) {
-
- assert(threadID >= 0 && threadID < TM.active_threads());
- assert(TM.active_threads() > 1);
-
- Position pos(*sp->pos);
- CheckInfo ci(pos);
- SearchStack* ss = sp->sstack[threadID];
- Value value = -VALUE_INFINITE;
- Move move;
- int moveCount;
- bool isCheck = pos.is_check();
- bool useFutilityPruning = sp->depth < 7 * OnePly //FIXME: sync with search
- && !isCheck;
-
- while ( lock_grab_bool(&(sp->lock))
- && sp->bestValue < sp->beta
- && !TM.thread_should_stop(threadID)
- && (move = sp->mp->get_next_move()) != MOVE_NONE)
- {
- moveCount = ++sp->moves;
- lock_release(&(sp->lock));
-
- assert(move_is_ok(move));
-
- bool moveIsCheck = pos.move_is_check(move, ci);
- bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- ss[sp->ply].currentMove = move;
-
- // Decide the new search depth
- bool dangerous;
- Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
- Depth newDepth = sp->depth - OnePly + ext;
-
- // Prune?
- if ( useFutilityPruning
- && !dangerous
- && !captureOrPromotion)
- {
- // 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))
- continue;
-
- // Value based pruning
- Value futilityValueScaled = sp->futilityValue - moveCount * 8; //FIXME: sync with search
-
- if (futilityValueScaled < sp->beta)
- {
- if (futilityValueScaled > sp->bestValue) // Less then 1% of cases
- {
- lock_grab(&(sp->lock));
- if (futilityValueScaled > sp->bestValue)
- sp->bestValue = futilityValueScaled;
- lock_release(&(sp->lock));
- }
- continue;
- }
- }
-
- // Make and search the move.
- StateInfo st;
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Try to reduce non-pv search depth by one ply if move seems not problematic,
- // 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 = nonpv_reduction(sp->depth, moveCount);
- if (ss[sp->ply].reduction)
- {
- value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
- doFullDepthSearch = (value >= sp->beta);
- }
- }
-
- if (doFullDepthSearch) // Go with full depth non-pv search
- {
- ss[sp->ply].reduction = Depth(0);
- value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
- }
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- if (TM.thread_should_stop(threadID))
- {
- lock_grab(&(sp->lock));
- break;
- }
-
- // New best move?
- if (value > sp->bestValue) // Less then 2% of cases
- {
- lock_grab(&(sp->lock));
- if (value > sp->bestValue && !TM.thread_should_stop(threadID))
- {
- sp->bestValue = value;
- if (sp->bestValue >= sp->beta)
- {
- sp_update_pv(sp->parentSstack, ss, sp->ply);
- for (int i = 0; i < TM.active_threads(); i++)
- if (i != threadID && (i == sp->master || sp->slaves[i]))
- TM.set_stop_request(i);
-
- sp->finished = true;
- }
- }
- lock_release(&(sp->lock));
- }
- }
-
- /* Here we have the lock still grabbed */
-
- // If this is the master thread and we have been asked to stop because of
- // a beta cutoff higher up in the tree, stop all slave threads. Note that
- // thread_should_stop(threadID) does not imply that 'stop' flag is set, so
- // do this explicitly now, under lock protection.
- if (sp->master == threadID && TM.thread_should_stop(threadID))
- for (int i = 0; i < TM.active_threads(); i++)
- if (sp->slaves[i] || i == threadID)
- TM.set_stop_request(i);
-
- sp->cpus--;
- sp->slaves[threadID] = 0;
-
- lock_release(&(sp->lock));
- }
-
-
- // sp_search_pv() is used to search from a PV split point. This function
- // is called by each thread working at the split point. It is similar to
- // the normal search_pv() function, but simpler. Because we have already
- // probed the hash table and searched the first move before splitting, we
- // don't have to repeat all this work in sp_search_pv(). We also don't
- // need to store anything to the hash table here: This is taken care of
- // after we return from the split point.
-
- void sp_search_pv(SplitPoint* sp, int threadID) {
-
- assert(threadID >= 0 && threadID < TM.active_threads());
- assert(TM.active_threads() > 1);
-
- Position pos(*sp->pos);
- CheckInfo ci(pos);
- SearchStack* ss = sp->sstack[threadID];
- Value value = -VALUE_INFINITE;
- int moveCount;
- Move move;
-
- while ( lock_grab_bool(&(sp->lock))
- && sp->alpha < sp->beta
- && !TM.thread_should_stop(threadID)
- && (move = sp->mp->get_next_move()) != MOVE_NONE)
- {
- moveCount = ++sp->moves;
- lock_release(&(sp->lock));
-
- assert(move_is_ok(move));
-
- bool moveIsCheck = pos.move_is_check(move, ci);
- bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- ss[sp->ply].currentMove = move;
-
- // Decide the new search depth
- bool dangerous;
- Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
- Depth newDepth = sp->depth - OnePly + ext;
-
- // Make and search the move.
- StateInfo st;
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Try to reduce non-pv search depth by one ply if move seems not problematic,
- // if the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;