Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
template <NodeType PvNode>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
+ Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID);
template <NodeType PvNode>
Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID);
alpha = -VALUE_INFINITE;
// Full depth PV search, done on first move or after a fail high
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, 0);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 0);
}
else
{
if (ss->reduction)
{
// Reduced depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, 0);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 0);
doFullDepthSearch = (value > alpha);
}
}
{
// Full depth non-pv search using alpha as upperbound
ss->reduction = Depth(0);
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, true, 0);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 0);
// If we are above alpha then research at same depth but as PV
// to get a correct score or eventually a fail high above beta.
if (value > alpha)
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, 0);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 0);
}
}
// search<>() is the main search function for both PV and non-PV nodes
template <NodeType PvNode>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth,
- bool allowNullmove, int threadID, Move excludedMove) {
+ Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID) {
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
EvalInfo ei;
StateInfo st;
const TTEntry* tte;
- Move ttMove, move;
+ Key posKey;
+ Move ttMove, move, excludedMove;
Depth ext, newDepth;
Value bestValue, value, oldAlpha;
Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific
// Step 1. Initialize node and poll. Polling can abort search
TM.incrementNodeCounter(threadID);
ss->init(ply);
+ (ss + 1)->excludedMove = MOVE_NONE;
+ (ss + 1)->skipNullMove = false;
(ss + 2)->initKillers();
if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
// We don't want the score of a partial search to overwrite a previous full search
// TT value, so we use a different position key in case of an excluded move exists.
- Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
+ excludedMove = ss->excludedMove;
+ posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
tte = TT.retrieve(posKey);
ttMove = (tte ? tte->move() : MOVE_NONE);
// We're betting that the opponent doesn't have a move that will reduce
// the score by more than futility_margin(depth) if we do a null move.
if ( !PvNode
- && allowNullmove
+ && !ss->skipNullMove
&& depth < RazorDepth
&& refinedValue >= beta + futility_margin(depth, 0)
&& !isCheck
// at least beta. Otherwise we do a null move if static value is not more than
// NullMoveMargin under beta.
if ( !PvNode
- && allowNullmove
+ && !ss->skipNullMove
&& depth > OnePly
&& refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0)
&& !isCheck
pos.do_null_move(st);
+ (ss+1)->skipNullMove = true;
+
nullValue = depth-R*OnePly < OnePly ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly, false, threadID);
+ : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly, threadID);
+
+ (ss+1)->skipNullMove = false;
+
pos.undo_null_move();
if (nullValue >= beta)
nullValue = beta;
// Do zugzwang verification search at high depths
- if ( depth < 6 * OnePly
- || search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, false, threadID) >= beta)
+ if (depth < 6 * OnePly)
+ return nullValue;
+
+ ss->skipNullMove = true;
+ Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, threadID);
+ ss->skipNullMove = false;
+
+ if (v >= beta)
return nullValue;
}
else
&& (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
{
Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
- search<PvNode>(pos, ss, alpha, beta, d, false, threadID);
+
+ ss->skipNullMove = true;
+ search<PvNode>(pos, ss, alpha, beta, d, threadID);
+ ss->skipNullMove = false;
+
ttMove = ss->pv[ply];
tte = TT.retrieve(posKey);
}
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
Value b = ttValue - SingularExtensionMargin;
- Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, false, threadID, move);
+ ss->excludedMove = move;
+ ss->skipNullMove = true;
+ Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, threadID);
+ ss->skipNullMove = false;
+ ss->excludedMove = MOVE_NONE;
if (v < ttValue - SingularExtensionMargin)
ext = OnePly;
// The first move in list is the expected PV
if (PvNode && moveCount == 1)
value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0), threadID)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, threadID);
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, threadID);
else
{
// Step 14. Reduced depth search
{
Depth d = newDepth - ss->reduction;
value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true, threadID);
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, threadID);
doFullDepthSearch = (value > alpha);
}
assert(newDepth - OnePly >= OnePly);
ss->reduction = OnePly;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, threadID);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, threadID);
doFullDepthSearch = (value > alpha);
}
ss->reduction = Depth(0); // Restore original reduction
if (doFullDepthSearch)
{
value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, true, threadID);
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, threadID);
// 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 > alpha && value < beta)
value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0), threadID)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, threadID);
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, threadID);
}
}
// Step 12. Futility pruning (is omitted in PV nodes)
if ( !PvNode
+ && !captureOrPromotion
&& !isCheck
&& !dangerous
- && !captureOrPromotion
&& !move_is_castle(move))
{
// Move count based pruning
// If the move fails high will be re-searched at full depth.
bool doFullDepthSearch = true;
- if ( !dangerous
- && !captureOrPromotion
+ if ( !captureOrPromotion
+ && !dangerous
&& !move_is_castle(move)
&& !move_is_killer(move, ss))
{
if (ss->reduction)
{
Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, true, threadID);
+ Depth d = newDepth - ss->reduction;
+ value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), threadID)
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d, threadID);
doFullDepthSearch = (value > localAlpha);
}
// if the move fails high again then go with full depth search.
if (doFullDepthSearch && ss->reduction > 2 * OnePly)
{
+ assert(newDepth - OnePly >= OnePly);
+
ss->reduction = OnePly;
Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, true, threadID);
+ value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, threadID);
doFullDepthSearch = (value > localAlpha);
}
+ ss->reduction = Depth(0); // Restore original reduction
}
// Step 15. Full depth search
if (doFullDepthSearch)
{
- ss->reduction = Depth(0);
Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, true, threadID);
+ value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), threadID)
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, threadID);
+ // 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 < sp->beta)
- value = -search<PV>(pos, ss+1, -sp->beta, -sp->alpha, newDepth, false, threadID);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -sp->beta, -sp->alpha, Depth(0), threadID)
+ : - search<PV>(pos, ss+1, -sp->beta, -sp->alpha, newDepth, threadID);
}
// Step 16. Undo move
{
ss->init(i);
ss->initKillers();
+ ss->excludedMove = MOVE_NONE;
+ ss->skipNullMove = false;
}
}