return search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
}
+ template <NodeType PvNode>
+ void sp_search(Position& pos, SearchStack* ss, Value, Value beta, Depth depth, int ply);
+
template <NodeType PvNode>
Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
int64_t nodes;
Move move;
Depth depth, ext, newDepth;
- Value value, alpha, beta;
+ Value value, evalMargin, alpha, beta;
bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
int researchCountFH, researchCountFL;
// Step 5. Evaluate the position statically
// At root we do this only to get reference value for child nodes
- ss->evalMargin = VALUE_NONE;
- ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
+ ss->eval = isCheck ? VALUE_NONE : evaluate(pos, evalMargin);
// Step 6. Razoring (omitted at root)
// Step 7. Static null move pruning (omitted at root)
Key posKey;
Move ttMove, move, excludedMove, threatMove;
Depth ext, newDepth;
- Value bestValue, value, oldAlpha;
+ Value bestValue, value, evalMargin, oldAlpha;
Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
bool mateThreat = false;
{
sp = ss->sp;
tte = NULL;
+ evalMargin = VALUE_ZERO;
ttMove = excludedMove = MOVE_NONE;
threatMove = sp->threatMove;
mateThreat = sp->mateThreat;
// Step 5. Evaluate the position statically and
// update gain statistics of parent move.
if (isCheck)
- ss->eval = ss->evalMargin = VALUE_NONE;
+ ss->eval = evalMargin = VALUE_NONE;
else if (tte)
{
assert(tte->static_value() != VALUE_NONE);
ss->eval = tte->static_value();
- ss->evalMargin = tte->static_value_margin();
+ evalMargin = tte->static_value_margin();
refinedValue = refine_eval(tte, ss->eval, ply);
}
else
{
- refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
- TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
+ refinedValue = ss->eval = evaluate(pos, evalMargin);
+ TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
}
// Save gain for the parent non-capture move
CheckInfo ci(pos);
ss->bestMove = MOVE_NONE;
singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
- futilityBase = ss->eval + ss->evalMargin;
+ futilityBase = ss->eval + evalMargin;
singularExtensionNode = !SpNode
&& depth >= SingularExtensionDepth[PvNode]
&& tte
if (value > bestValue && !(SpNode && ThreadsMgr.thread_should_stop(threadID)))
{
bestValue = value;
+
+ if (SpNode)
+ sp->bestValue = value;
+
if (value > alpha)
{
if (SpNode && (!PvNode || value >= beta))
sp->stopRequest = true;
if (PvNode && value < beta) // We want always alpha < beta
+ {
alpha = value;
+ if (SpNode)
+ sp->alpha = value;
+ }
if (value == value_mate_in(ply + 1))
ss->mateKiller = move;
ss->bestMove = move;
- }
- if (SpNode)
- {
- sp->bestValue = bestValue;
- sp->alpha = alpha;
- sp->parentSstack->bestMove = ss->bestMove;
+
+ if (SpNode)
+ sp->parentSstack->bestMove = move;
}
}
ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
move = (bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove);
- TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
+ TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, evalMargin);
// Update killers and history only for non capture moves that fails high
if ( bestValue >= beta
}
+ // 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.
+
+ template <NodeType PvNode>
+ void sp_search(Position& pos, SearchStack* ss, Value, Value beta, Depth depth, int ply) {
+
+ StateInfo st;
+ Move move;
+ Depth ext, newDepth;
+ Value value;
+ Value futilityValueScaled; // NonPV specific
+ bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
+ int moveCount;
+ value = -VALUE_INFINITE;
+ SplitPoint* sp = ss->sp;
+ Move threatMove = sp->threatMove;
+ MovePicker& mp = *sp->mp;
+ int threadID = pos.thread();
+
+ CheckInfo ci(pos);
+ isCheck = pos.is_check();
+
+ // Step 10. Loop through moves
+ // Loop through all legal moves until no moves remain or a beta cutoff occurs
+ lock_grab(&(sp->lock));
+
+ while ( sp->bestValue < beta
+ && (move = mp.get_next_move()) != MOVE_NONE
+ && !ThreadsMgr.thread_should_stop(threadID))
+ {
+ 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 = depth - ONE_PLY + ext;
+
+ // Update current move
+ ss->currentMove = move;
+
+ // Step 12. Futility pruning (is omitted in PV nodes)
+ if ( !PvNode
+ && !captureOrPromotion
+ && !isCheck
+ && !dangerous
+ && !move_is_castle(move))
+ {
+ // Move count based pruning
+ if ( moveCount >= futility_move_count(depth)
+ && !(threatMove && connected_threat(pos, move, threatMove))
+ && sp->bestValue > value_mated_in(PLY_MAX))
+ {
+ lock_grab(&(sp->lock));
+ continue;
+ }
+
+ // Value based pruning
+ Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
+ futilityValueScaled = ss->eval + futility_margin(predictedDepth, moveCount)
+ + H.gain(pos.piece_on(move_from(move)), move_to(move));
+
+ if (futilityValueScaled < 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 ( !captureOrPromotion
+ && !dangerous
+ && !move_is_castle(move)
+ && !(ss->killers[0] == move || ss->killers[1] == move))
+ {
+ ss->reduction = reduction<PvNode>(depth, moveCount);
+ if (ss->reduction)
+ {
+ Value localAlpha = sp->alpha;
+ Depth d = newDepth - ss->reduction;
+ value = d < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, DEPTH_ZERO, ply+1)
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d, ply+1);
+
+ doFullDepthSearch = (value > localAlpha);
+ }
+
+ // The move failed high, but if reduction is very big we could
+ // face a false positive, retry with a less aggressive reduction,
+ // if the move fails high again then go with full depth search.
+ if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY)
+ {
+ assert(newDepth - ONE_PLY >= ONE_PLY);
+
+ ss->reduction = ONE_PLY;
+ Value localAlpha = sp->alpha;
+ value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, ply+1);
+ doFullDepthSearch = (value > localAlpha);
+ }
+ ss->reduction = DEPTH_ZERO; // Restore original reduction
+ }
+
+ // Step 15. Full depth search
+ if (doFullDepthSearch)
+ {
+ Value localAlpha = sp->alpha;
+ value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, DEPTH_ZERO, ply+1)
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, ply+1);
+
+ // Step extra. pv search (only in PV nodes)
+ // Search only for possible new PV nodes, if instead value >= beta then
+ // parent node fails low with value <= alpha and tries another move.
+ if (PvNode && value > localAlpha && value < beta)
+ value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -sp->alpha, DEPTH_ZERO, ply+1)
+ : - search<PV>(pos, ss+1, -beta, -sp->alpha, newDepth, ply+1);
+ }
+
+ // 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 && !ThreadsMgr.thread_should_stop(threadID))
+ {
+ sp->bestValue = value;
+ if (value > sp->alpha)
+ {
+ if (!PvNode || value >= beta)
+ sp->stopRequest = true;
+
+ if (PvNode && value < beta) // We want always sp->alpha < beta
+ sp->alpha = value;
+
+ sp->parentSstack->bestMove = ss->bestMove = move;
+ }
+ }
+ }
+
+ /* Here we have the lock still grabbed */
+
+ sp->slaves[threadID] = 0;
+
+ lock_release(&(sp->lock));
+ }
+
+
// connected_moves() tests whether two moves are 'connected' in the sense
// that the first move somehow made the second move possible (for instance
// if the moving piece is the same in both moves). The first move is assumed
ss->sp = tsp;
if (tsp->pvNode)
- search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+ //search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+ sp_search<PV>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
else
- search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+ //search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+ sp_search<NonPV>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
assert(threads[threadID].state == THREAD_SEARCHING);
// Initialize search stack
init_ss_array(ss, PLY_MAX_PLUS_2);
- ss[0].eval = ss[0].evalMargin = VALUE_NONE;
+ ss[0].eval = VALUE_NONE;
count = 0;
// Generate all legal moves
projects / stockfish / blobdiff