namespace {
/// Types
-
+ enum NodeType { NonPV, PV };
// ThreadsManager class is used to handle all the threads related stuff in search,
// init, starting, parking and, the most important, launching a slave thread at a
// Step 9. Internal iterative deepening
// Minimum depth for use of internal iterative deepening
- const Depth IIDDepthAtPVNodes = 5 * OnePly;
- const Depth IIDDepthAtNonPVNodes = 8 * OnePly;
+ const Depth IIDDepth[2] = { 8 * OnePly /* non-PV */, 5 * OnePly /* PV */};
// At Non-PV nodes we do an internal iterative deepening search
// when the static evaluation is at most IIDMargin below beta.
Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
// Minimum depth for use of singular extension
- const Depth SingularExtensionDepthAtPVNodes = 6 * OnePly;
- const Depth SingularExtensionDepthAtNonPVNodes = 8 * OnePly;
+ const Depth SingularExtensionDepth[2] = { 8 * OnePly /* non-PV */, 6 * OnePly /* PV */};
// If the TT move is at least SingularExtensionMargin better then the
// remaining ones we will extend it.
// Step 14. Reduced search
// Reduction lookup tables (initialized at startup) and their getter functions
- int8_t PVReductionMatrix[64][64]; // [depth][moveNumber]
- int8_t NonPVReductionMatrix[64][64]; // [depth][moveNumber]
+ int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
- inline Depth pv_reduction(Depth d, int mn) { return (Depth) PVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; }
- inline Depth nonpv_reduction(Depth d, int mn) { return (Depth) NonPVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; }
+ template <NodeType PV>
+ inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
// Common adjustments
Value id_loop(const Position& pos, Move searchMoves[]);
Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
- Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
- Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
+
+ template <NodeType PvNode>
+ Value search(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
+
+ template <NodeType PvNode>
Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
+
+ template <NodeType PvNode>
+ Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
+
void sp_search(SplitPoint* sp, int threadID);
void sp_search_pv(SplitPoint* sp, int threadID);
void init_node(SearchStack ss[], int ply, int threadID);
bool connected_moves(const Position& pos, Move m1, Move m2);
bool value_is_mate(Value value);
bool move_is_killer(Move m, const SearchStack& ss);
- Depth extension(const Position&, Move, bool, bool, bool, bool, bool, bool*);
bool ok_to_do_nullmove(const Position& pos);
bool ok_to_prune(const Position& pos, Move m, Move threat);
bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
{
double pvRed = log(double(i)) * log(double(j)) / 3.0;
double nonPVRed = log(double(i)) * log(double(j)) / 1.5;
- PVReductionMatrix[i][j] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0);
- NonPVReductionMatrix[i][j] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0);
+ ReductionMatrix[PV][i][j] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0);
+ ReductionMatrix[NonPV][i][j] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0);
}
// Init futility margins array
// Step 11. Decide the new search depth
depth = (Iteration - 2) * OnePly + InitialDepth;
- ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
+ ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
newDepth = depth + ext;
// Step 12. Futility pruning (omitted at root)
alpha = -VALUE_INFINITE;
// Full depth PV search, done on first move or after a fail high
- value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
+ value = -search<PV>(pos, ss, -beta, -alpha, newDepth, 1, false, 0);
}
else
{
&& !captureOrPromotion
&& !move_is_castle(move))
{
- ss[0].reduction = pv_reduction(depth, i - MultiPV + 2);
+ ss[0].reduction = reduction<PV>(depth, i - MultiPV + 2);
if (ss[0].reduction)
{
// Reduced depth non-pv search using alpha as upperbound
- value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
+ value = -search<NonPV>(pos, ss, -(alpha+1), -alpha, newDepth-ss[0].reduction, 1, true, 0);
doFullDepthSearch = (value > alpha);
}
}
{
// Full depth non-pv search using alpha as upperbound
ss[0].reduction = Depth(0);
- value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
+ value = -search<NonPV>(pos, ss, -(alpha+1), -alpha, newDepth, 1, true, 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, -beta, -alpha, newDepth, 1, 0);
+ value = -search<PV>(pos, ss, -beta, -alpha, newDepth, 1, false, 0);
}
}
}
- // search_pv() is the main search function for PV nodes.
+ // search<>() is the main search function for both PV and non-PV nodes
- Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta,
- Depth depth, int ply, int threadID) {
+ template <NodeType PvNode>
+ Value search(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth,
+ int ply, bool allowNullmove, int threadID, Move excludedMove) {
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
+ assert(PvNode || alpha == beta - 1);
assert(ply >= 0 && ply < PLY_MAX);
assert(threadID >= 0 && threadID < TM.active_threads());
Move ttMove, move;
Depth ext, newDepth;
Value bestValue, value, oldAlpha;
+ Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific
bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
bool mateThreat = false;
int moveCount = 0;
- bestValue = value = -VALUE_INFINITE;
+ refinedValue = bestValue = value = -VALUE_INFINITE;
+ oldAlpha = alpha;
if (depth < OnePly)
- return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
+ return qsearch<PvNode>(pos, ss, alpha, beta, Depth(0), ply, threadID);
// Step 1. Initialize node and poll
// Polling can abort search.
return VALUE_DRAW;
// Step 3. Mate distance pruning
- oldAlpha = alpha;
alpha = Max(value_mated_in(ply), alpha);
beta = Min(value_mate_in(ply+1), beta);
if (alpha >= beta)
return alpha;
- // Step 4. Transposition table lookup
- // At PV nodes, we don't use the TT for pruning, but only for move ordering.
- // This is to avoid problems in the following areas:
- //
- // * Repetition draw detection
- // * Fifty move rule detection
- // * Searching for a mate
- // * Printing of full PV line
- tte = TT.retrieve(pos.get_key());
- ttMove = (tte ? tte->move() : MOVE_NONE);
-
- // Step 5. Evaluate the position statically
- // At PV nodes we do this only to update gain statistics
- isCheck = pos.is_check();
- if (!isCheck)
- {
- ss[ply].eval = evaluate(pos, ei, threadID);
- update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
- }
-
- // Step 6. Razoring (is omitted in PV nodes)
- // Step 7. Static null move pruning (is omitted in PV nodes)
- // Step 8. Null move search with verification search (is omitted in PV nodes)
-
- // Step 9. Internal iterative deepening
- if ( depth >= IIDDepthAtPVNodes
- && ttMove == MOVE_NONE)
- {
- search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
- ttMove = ss[ply].pv[ply];
- tte = TT.retrieve(pos.get_key());
- }
-
- // Initialize a MovePicker object for the current position
- mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
- MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
- CheckInfo ci(pos);
-
- // Step 10. Loop through moves
- // Loop through all legal moves until no moves remain or a beta cutoff occurs
- while ( alpha < beta
- && (move = mp.get_next_move()) != MOVE_NONE
- && !TM.thread_should_stop(threadID))
- {
- assert(move_is_ok(move));
-
- singleEvasion = (isCheck && mp.number_of_evasions() == 1);
- moveIsCheck = pos.move_is_check(move, ci);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- // Step 11. Decide the new search depth
- ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
-
- // Singular extension search. We extend the TT move if its value is much better than
- // its siblings. To verify this we do a reduced search on all the other moves but the
- // ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
- if ( depth >= SingularExtensionDepthAtPVNodes
- && tte
- && move == tte->move()
- && ext < OnePly
- && is_lower_bound(tte->type())
- && tte->depth() >= depth - 3 * OnePly)
- {
- Value ttValue = value_from_tt(tte->value(), ply);
-
- if (abs(ttValue) < VALUE_KNOWN_WIN)
- {
- Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
-
- if (excValue < ttValue - SingularExtensionMargin)
- ext = OnePly;
- }
- }
-
- newDepth = depth - OnePly + ext;
-
- // Update current move (this must be done after singular extension search)
- movesSearched[moveCount++] = ss[ply].currentMove = move;
-
- // Step 12. Futility pruning (is omitted in PV nodes)
-
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Step extra. pv search (only in PV nodes)
- // The first move in list is the expected PV
- if (moveCount == 1)
- value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
- else
- {
- // Step 14. Reduced search
- // if the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
-
- if ( depth >= 3 * OnePly
- && !dangerous
- && !captureOrPromotion
- && !move_is_castle(move)
- && !move_is_killer(move, ss[ply]))
- {
- ss[ply].reduction = pv_reduction(depth, moveCount);
- if (ss[ply].reduction)
- {
- value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
- doFullDepthSearch = (value > alpha);
- }
- }
-
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- ss[ply].reduction = Depth(0);
- value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
-
- // Step extra. pv search (only in PV nodes)
- if (value > alpha && value < beta)
- value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
- }
- }
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- // Step 17. Check for new best move
- if (value > bestValue)
- {
- bestValue = value;
- if (value > alpha)
- {
- alpha = value;
- update_pv(ss, ply);
- if (value == value_mate_in(ply + 1))
- ss[ply].mateKiller = move;
- }
- }
-
- // Step 18. Check for split
- if ( TM.active_threads() > 1
- && bestValue < beta
- && depth >= MinimumSplitDepth
- && Iteration <= 99
- && TM.available_thread_exists(threadID)
- && !AbortSearch
- && !TM.thread_should_stop(threadID)
- && TM.split(pos, ss, ply, &alpha, beta, &bestValue,
- depth, mateThreat, &moveCount, &mp, threadID, true))
- break;
- }
-
- // Step 19. Check for mate and stalemate
- // All legal moves have been searched and if there were
- // no legal moves, it must be mate or stalemate.
- if (moveCount == 0)
- return (isCheck ? value_mated_in(ply) : VALUE_DRAW);
-
- // Step 20. Update tables
- // If the search is not aborted, update the transposition table,
- // history counters, and killer moves.
- if (AbortSearch || TM.thread_should_stop(threadID))
- return bestValue;
-
- if (bestValue <= oldAlpha)
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
-
- else if (bestValue >= beta)
- {
- TM.incrementBetaCounter(pos.side_to_move(), depth, threadID);
- move = ss[ply].pv[ply];
- if (!pos.move_is_capture_or_promotion(move))
- {
- update_history(pos, move, depth, movesSearched, moveCount);
- update_killers(move, ss[ply]);
- }
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move);
- }
- else
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]);
-
- return bestValue;
- }
-
-
- // search() is the search function for zero-width nodes.
-
- Value search(Position& pos, SearchStack ss[], Value beta, Depth depth,
- int ply, bool allowNullmove, int threadID, Move excludedMove) {
-
- assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
- assert(ply >= 0 && ply < PLY_MAX);
- assert(threadID >= 0 && threadID < TM.active_threads());
-
- Move movesSearched[256];
- EvalInfo ei;
- StateInfo st;
- const TTEntry* tte;
- Move ttMove, move;
- Depth ext, newDepth;
- Value bestValue, refinedValue, nullValue, value, futilityValueScaled;
- bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
- bool mateThreat = false;
- int moveCount = 0;
- refinedValue = bestValue = value = -VALUE_INFINITE;
-
- if (depth < OnePly)
- return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
-
- // Step 1. Initialize node and poll
- // Polling can abort search.
- init_node(ss, ply, threadID);
-
- // Step 2. Check for aborted search and immediate draw
- if (AbortSearch || TM.thread_should_stop(threadID))
- return Value(0);
-
- if (pos.is_draw() || ply >= PLY_MAX - 1)
- return VALUE_DRAW;
-
- // Step 3. Mate distance pruning
- if (value_mated_in(ply) >= beta)
- return beta;
-
- if (value_mate_in(ply + 1) < beta)
- return beta - 1;
-
// Step 4. Transposition table lookup
// We don't want the score of a partial search to overwrite a previous full search
tte = TT.retrieve(posKey);
ttMove = (tte ? tte->move() : MOVE_NONE);
- if (tte && ok_to_use_TT(tte, depth, beta, ply))
+ // At PV nodes, we don't use the TT for pruning, but only for move ordering.
+ // This is to avoid problems in the following areas:
+ //
+ // * Repetition draw detection
+ // * Fifty move rule detection
+ // * Searching for a mate
+ // * Printing of full PV line
+
+ if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
{
// Refresh tte entry to avoid aging
TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove);
}
// Step 5. Evaluate the position statically
+ // At PV nodes we do this only to update gain statistics
isCheck = pos.is_check();
-
if (!isCheck)
{
if (tte && (tte->type() & VALUE_TYPE_EVAL))
update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
}
- // Step 6. Razoring
- if ( refinedValue < beta - razor_margin(depth)
+ // Step 6. Razoring (is omitted in PV nodes)
+ if ( !PvNode
+ && refinedValue < beta - razor_margin(depth)
&& ttMove == MOVE_NONE
&& ss[ply - 1].currentMove != MOVE_NULL
&& depth < RazorDepth
&& !pos.has_pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
+ Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
if (v < rbeta)
// Logically we should return (v + razor_margin(depth)), but
// surprisingly this did slightly weaker in tests.
return v;
}
- // Step 7. Static null move pruning
+ // Step 7. Static null move pruning (is omitted in PV nodes)
// 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 ( allowNullmove
+ if ( !PvNode
+ && allowNullmove
&& depth < RazorDepth
&& !isCheck
&& !value_is_mate(beta)
&& refinedValue >= beta + futility_margin(depth, 0))
return refinedValue - futility_margin(depth, 0);
- // Step 8. Null move search with verification search
+ // Step 8. Null move search with verification search (is omitted in PV nodes)
// When we jump directly to qsearch() we do a null move only if static value is
// at least beta. Otherwise we do a null move if static value is not more than
// NullMoveMargin under beta.
- if ( allowNullmove
+ if ( !PvNode
+ && allowNullmove
&& depth > OnePly
&& !isCheck
&& !value_is_mate(beta)
pos.do_null_move(st);
- nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
+ nullValue = -search<NonPV>(pos, ss, -beta, -alpha, depth-R*OnePly, ply+1, false, threadID);
pos.undo_null_move();
return nullValue;
// Do zugzwang verification search
- Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
+ Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, ply, false, threadID);
if (v >= beta)
return nullValue;
} else {
}
// Step 9. Internal iterative deepening
- if ( depth >= IIDDepthAtNonPVNodes
+ if ( depth >= IIDDepth[PvNode]
&& ttMove == MOVE_NONE
- && !isCheck
- && ss[ply].eval >= beta - IIDMargin)
+ && (PvNode || (!isCheck && ss[ply].eval >= beta - IIDMargin)))
{
- search(pos, ss, beta, depth/2, ply, false, threadID);
+ Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
+ search<PvNode>(pos, ss, alpha, beta, d, ply, false, threadID);
ttMove = ss[ply].pv[ply];
tte = TT.retrieve(posKey);
}
+ // Expensive mate threat detection (only for PV nodes)
+ if (PvNode)
+ mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
+
// Initialize a MovePicker object for the current position
- MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], beta);
+ MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], (PvNode ? -VALUE_INFINITE : beta));
CheckInfo ci(pos);
// Step 10. Loop through moves
if (move == excludedMove)
continue;
- moveIsCheck = pos.move_is_check(move, ci);
singleEvasion = (isCheck && mp.number_of_evasions() == 1);
+ moveIsCheck = pos.move_is_check(move, ci);
captureOrPromotion = pos.move_is_capture_or_promotion(move);
// Step 11. Decide the new search depth
- ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
+ ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
// Singular extension search. We extend the TT move if its value is much better than
// its siblings. To verify this we do a reduced search on all the other moves but the
// ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
- if ( depth >= SingularExtensionDepthAtNonPVNodes
+ if ( depth >= SingularExtensionDepth[PvNode]
&& tte
&& move == tte->move()
&& !excludedMove // Do not allow recursive singular extension search
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
+ Value b = ttValue - SingularExtensionMargin;
+ Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply, false, threadID, move);
- if (excValue < ttValue - SingularExtensionMargin)
+ if (v < ttValue - SingularExtensionMargin)
ext = OnePly;
}
}
// Update current move (this must be done after singular extension search)
movesSearched[moveCount++] = ss[ply].currentMove = move;
- // Step 12. Futility pruning
- if ( !isCheck
+ // Step 12. Futility pruning (is omitted in PV nodes)
+ if ( !PvNode
+ && !isCheck
&& !dangerous
&& !captureOrPromotion
&& !move_is_castle(move)
continue;
// Value based pruning
- Depth predictedDepth = newDepth - nonpv_reduction(depth, moveCount); // We illogically ignore reduction condition depth >= 3*OnePly
+ Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount); // FIXME We illogically ignore reduction condition depth >= 3*OnePly
futilityValueScaled = ss[ply].eval + futility_margin(predictedDepth, moveCount)
+ H.gain(pos.piece_on(move_from(move)), move_to(move));
// 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 ( depth >= 3*OnePly
- && !dangerous
- && !captureOrPromotion
- && !move_is_castle(move)
- && !move_is_killer(move, ss[ply]))
+ // Step extra. pv search (only in PV nodes)
+ // The first move in list is the expected PV
+ if (PvNode && moveCount == 1)
+ value = -search<PV>(pos, ss, -beta, -alpha, newDepth, ply+1, false, threadID);
+ else
{
- ss[ply].reduction = nonpv_reduction(depth, moveCount);
- if (ss[ply].reduction)
+ // Step 14. Reduced search
+ // if the move fails high will be re-searched at full depth.
+ bool doFullDepthSearch = true;
+
+ if ( depth >= 3 * OnePly
+ && !dangerous
+ && !captureOrPromotion
+ && !move_is_castle(move)
+ && !move_is_killer(move, ss[ply]))
{
- value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
- doFullDepthSearch = (value >= beta);
+ ss[ply].reduction = reduction<PvNode>(depth, moveCount);
+ if (ss[ply].reduction)
+ {
+ value = -search<NonPV>(pos, ss, -(alpha+1), -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
+ doFullDepthSearch = (value > alpha);
+ }
}
- }
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- ss[ply].reduction = Depth(0);
- value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
+ // Step 15. Full depth search
+ if (doFullDepthSearch)
+ {
+ ss[ply].reduction = Depth(0);
+ value = -search<NonPV>(pos, ss, -(alpha+1), -alpha, newDepth, ply+1, true, 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 = -search<PV>(pos, ss, -beta, -alpha, newDepth, ply+1, false, threadID);
+ }
}
// Step 16. Undo move
if (value > bestValue)
{
bestValue = value;
- if (value >= beta)
+ if (value > alpha)
+ {
+ alpha = value;
update_pv(ss, ply);
-
- if (value == value_mate_in(ply + 1))
- ss[ply].mateKiller = move;
+ if (value == value_mate_in(ply + 1))
+ ss[ply].mateKiller = move;
+ }
}
// Step 18. Check for split
&& TM.available_thread_exists(threadID)
&& !AbortSearch
&& !TM.thread_should_stop(threadID)
- && TM.split(pos, ss, ply, NULL, beta, &bestValue,
- depth, mateThreat, &moveCount, &mp, threadID, false))
+ && TM.split(pos, ss, ply, &alpha, beta, &bestValue,
+ depth, mateThreat, &moveCount, &mp, threadID, PvNode))
break;
}
// no legal moves, it must be mate or stalemate.
// If one move was excluded return fail low score.
if (!moveCount)
- return excludedMove ? beta - 1 : (isCheck ? value_mated_in(ply) : VALUE_DRAW);
+ return excludedMove ? oldAlpha : (isCheck ? value_mated_in(ply) : VALUE_DRAW);
// Step 20. Update tables
// If the search is not aborted, update the transposition table,
if (AbortSearch || TM.thread_should_stop(threadID))
return bestValue;
- if (bestValue < beta)
+ if (bestValue <= oldAlpha)
TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
- else
+
+ else if (bestValue >= beta)
{
TM.incrementBetaCounter(pos.side_to_move(), depth, threadID);
move = ss[ply].pv[ply];
update_history(pos, move, depth, movesSearched, moveCount);
update_killers(move, ss[ply]);
}
-
}
+ else
+ TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
// search function when the remaining depth is zero (or, to be more precise,
// less than OnePly).
+ template <NodeType PvNode>
Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta,
Depth depth, int ply, int threadID) {
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+ assert(PvNode || alpha == beta - 1);
assert(depth <= 0);
assert(ply >= 0 && ply < PLY_MAX);
assert(threadID >= 0 && threadID < TM.active_threads());
bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
const TTEntry* tte = NULL;
int moveCount = 0;
- bool pvNode = (beta - alpha != 1);
Value oldAlpha = alpha;
// Initialize, and make an early exit in case of an aborted search,
tte = TT.retrieve(pos.get_key());
ttMove = (tte ? tte->move() : MOVE_NONE);
- if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
+ if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
{
assert(tte->type() != VALUE_TYPE_EVAL);
ss[ply].currentMove = move;
// Futility pruning
- if ( enoughMaterial
+ if ( !PvNode
+ && enoughMaterial
&& !isCheck
- && !pvNode
&& !moveIsCheck
&& move != ttMove
&& !move_is_promotion(move)
&& !pos.can_castle(pos.side_to_move());
// Don't search moves with negative SEE values
- if ( (!isCheck || evasionPrunable)
- && !pvNode
+ if ( !PvNode
+ && (!isCheck || evasionPrunable)
&& move != ttMove
&& !move_is_promotion(move)
&& pos.see_sign(move) < 0)
// Make and search the move
pos.do_move(move, st, ci, moveIsCheck);
- value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
+ value = -qsearch<PvNode>(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
captureOrPromotion = pos.move_is_capture_or_promotion(move);
// Step 11. Decide the new search depth
- ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
+ ext = extension<NonPV>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
newDepth = sp->depth - OnePly + ext;
// Update current move
}
// Value based pruning
- Depth predictedDepth = newDepth - nonpv_reduction(sp->depth, moveCount);
+ 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));
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
- ss[sp->ply].reduction = nonpv_reduction(sp->depth, moveCount);
+ ss[sp->ply].reduction = reduction<NonPV>(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);
+ value = -search<NonPV>(pos, ss, -(sp->alpha+1), -(sp->alpha), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
doFullDepthSearch = (value >= sp->beta && !TM.thread_should_stop(threadID));
}
}
if (doFullDepthSearch)
{
ss[sp->ply].reduction = Depth(0);
- value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
+ value = -search<NonPV>(pos, ss, -(sp->alpha+1), -(sp->alpha), newDepth, sp->ply+1, true, threadID);
}
// Step 16. Undo move
captureOrPromotion = pos.move_is_capture_or_promotion(move);
// Step 11. Decide the new search depth
- ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
+ ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
newDepth = sp->depth - OnePly + ext;
// Update current move
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
- ss[sp->ply].reduction = pv_reduction(sp->depth, moveCount);
+ ss[sp->ply].reduction = reduction<PV>(sp->depth, moveCount);
if (ss[sp->ply].reduction)
{
Value localAlpha = sp->alpha;
- value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
+ value = -search<NonPV>(pos, ss, -(localAlpha+1), -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID));
}
}
{
Value localAlpha = sp->alpha;
ss[sp->ply].reduction = Depth(0);
- value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, true, threadID);
+ value = -search<NonPV>(pos, ss, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1, true, threadID);
if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID))
{
// to be higher or equal then beta, if so, avoid to start a PV search.
localAlpha = sp->alpha;
if (localAlpha < sp->beta)
- value = -search_pv(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, threadID);
+ value = -search<PV>(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, false, threadID);
}
}
// init_node() is called at the beginning of all the search functions
- // (search(), search_pv(), qsearch(), and so on) and initializes the
+ // (search() qsearch(), and so on) and initializes the
// search stack object corresponding to the current node. Once every
// NodesBetweenPolls nodes, init_node() also calls poll(), which polls
// for user input and checks whether it is time to stop the search.
// any case are marked as 'dangerous'. Note that also if a move is not
// extended, as example because the corresponding UCI option is set to zero,
// the move is marked as 'dangerous' so, at least, we avoid to prune it.
-
- Depth extension(const Position& pos, Move m, bool pvNode, bool captureOrPromotion,
- bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous) {
+ template <NodeType PvNode>
+ Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
+ bool singleEvasion, bool mateThreat, bool* dangerous) {
assert(m != MOVE_NONE);
if (*dangerous)
{
if (moveIsCheck)
- result += CheckExtension[pvNode];
+ result += CheckExtension[PvNode];
if (singleEvasion)
- result += SingleEvasionExtension[pvNode];
+ result += SingleEvasionExtension[PvNode];
if (mateThreat)
- result += MateThreatExtension[pvNode];
+ result += MateThreatExtension[PvNode];
}
if (pos.type_of_piece_on(move_from(m)) == PAWN)
Color c = pos.side_to_move();
if (relative_rank(c, move_to(m)) == RANK_7)
{
- result += PawnPushTo7thExtension[pvNode];
+ result += PawnPushTo7thExtension[PvNode];
*dangerous = true;
}
if (pos.pawn_is_passed(c, move_to(m)))
{
- result += PassedPawnExtension[pvNode];
+ result += PassedPawnExtension[PvNode];
*dangerous = true;
}
}
&& !move_is_promotion(m)
&& !move_is_ep(m))
{
- result += PawnEndgameExtension[pvNode];
+ result += PawnEndgameExtension[PvNode];
*dangerous = true;
}
- if ( pvNode
+ if ( PvNode
&& captureOrPromotion
&& pos.type_of_piece_on(move_to(m)) != PAWN
&& pos.see_sign(m) >= 0)
splitPoint->ply = ply;
splitPoint->depth = depth;
splitPoint->mateThreat = mateThreat;
- splitPoint->alpha = pvNode ? *alpha : beta - 1;
+ splitPoint->alpha = *alpha;
splitPoint->beta = beta;
splitPoint->pvNode = pvNode;
splitPoint->bestValue = *bestValue;
idle_loop(master, splitPoint);
// We have returned from the idle loop, which means that all threads are
- // finished. Update alpha, beta and bestValue, and return.
+ // finished. Update alpha and bestValue, and return.
lock_grab(&MPLock);
- if (pvNode)
- *alpha = splitPoint->alpha;
-
+ *alpha = splitPoint->alpha;
*bestValue = splitPoint->bestValue;
threads[master].activeSplitPoints--;
threads[master].splitPoint = splitPoint->parent;
init_ss_array(ss);
pos.do_move(cur->move, st);
moves[count].move = cur->move;
- moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
+ moves[count].score = -qsearch<PV>(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
moves[count].pv[0] = cur->move;
moves[count].pv[1] = MOVE_NONE;
pos.undo_move(cur->move);
projects / stockfish / blobdiff