void idle_loop(int threadID, SplitPoint* sp);
template <bool Fake>
- void split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
- Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, int master, bool pvNode);
+ void split(const Position& pos, SearchStack* ss, Value* alpha, const Value beta, Value* bestValue,
+ Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode);
private:
friend void poll();
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, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
+ Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
template <NodeType PvNode>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply, int threadID);
+ Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
template <NodeType PvNode>
void sp_search(SplitPoint* sp, int threadID);
template <NodeType PvNode>
Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
- void init_node(SearchStack* ss, int ply, int threadID);
void update_pv(SearchStack* ss, int ply);
void sp_update_pv(SearchStack* pss, SearchStack* ss, int ply);
bool connected_moves(const Position& pos, Move m1, Move m2);
bool value_is_mate(Value value);
bool move_is_killer(Move m, SearchStack* ss);
- 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);
+ bool connected_threat(const Position& pos, Move m, Move threat);
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
void update_killers(Move m, SearchStack* ss);
void poll();
void ponderhit();
void wait_for_stop_or_ponderhit();
- void init_ss_array(SearchStack* ss);
+ void init_ss_array(SearchStack* ss, int size);
void print_pv_info(const Position& pos, SearchStack* ss, Value alpha, Value beta, Value value);
#if !defined(_MSC_VER)
int64_t nodes_searched() { return TM.nodes_searched(); }
+/// init_search() is called during startup. It initializes various lookup tables
+
+void init_search() {
+
+ int d; // depth (OnePly == 2)
+ int hd; // half depth (OnePly == 1)
+ int mc; // moveCount
+
+ // Init reductions array
+ for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
+ {
+ double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
+ double nonPVRed = log(double(hd)) * log(double(mc)) / 1.5;
+ ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0);
+ ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0);
+ }
+
+ // Init futility margins array
+ for (d = 0; d < 16; d++) for (mc = 0; mc < 64; mc++)
+ FutilityMarginsMatrix[d][mc] = 112 * int(log(double(d * d) / 2) / log(2.0) + 1) - 8 * mc + 45;
+
+ // Init futility move count array
+ for (d = 0; d < 32; d++)
+ FutilityMoveCountArray[d] = 3 + (1 << (3 * d / 8));
+}
+
+
+// SearchStack::init() initializes a search stack. Used at the beginning of a
+// new search from the root.
+void SearchStack::init(int ply) {
+
+ pv[ply] = pv[ply + 1] = MOVE_NONE;
+ currentMove = threatMove = MOVE_NONE;
+ reduction = Depth(0);
+ eval = VALUE_NONE;
+}
+
+void SearchStack::initKillers() {
+
+ mateKiller = MOVE_NONE;
+ for (int i = 0; i < KILLER_MAX; i++)
+ killers[i] = MOVE_NONE;
+}
+
+
/// perft() is our utility to verify move generation is bug free. All the legal
/// moves up to given depth are generated and counted and the sum returned.
}
-/// init_search() is called during startup. It initializes various lookup tables
-
-void init_search() {
-
- // Init our reduction lookup tables
- for (int i = 1; i < 64; i++) // i == depth (OnePly = 1)
- for (int j = 1; j < 64; j++) // j == moveNumber
- {
- double pvRed = log(double(i)) * log(double(j)) / 3.0;
- double nonPVRed = log(double(i)) * log(double(j)) / 1.5;
- 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
- for (int i = 0; i < 16; i++) // i == depth (OnePly = 2)
- for (int j = 0; j < 64; j++) // j == moveNumber
- {
- // FIXME: test using log instead of BSR
- FutilityMarginsMatrix[i][j] = (i < 2 ? 0 : 112 * bitScanReverse32(i * i / 2)) - 8 * j + 45;
- }
-
- // Init futility move count array
- for (int i = 0; i < 32; i++) // i == depth (OnePly = 2)
- FutilityMoveCountArray[i] = 3 + (1 << (3 * i / 8));
-}
-
-
-// SearchStack::init() initializes a search stack. Used at the beginning of a
-// new search from the root.
-void SearchStack::init(int ply) {
-
- pv[ply] = pv[ply + 1] = MOVE_NONE;
- currentMove = threatMove = MOVE_NONE;
- reduction = Depth(0);
- eval = VALUE_NONE;
-}
-
-void SearchStack::initKillers() {
-
- mateKiller = MOVE_NONE;
- for (int i = 0; i < KILLER_MAX; i++)
- killers[i] = MOVE_NONE;
-}
-
namespace {
// id_loop() is the main iterative deepening loop. It calls root_search
Value id_loop(const Position& pos, Move searchMoves[]) {
- Position p(pos);
+ Position p(pos, pos.thread());
SearchStack ss[PLY_MAX_PLUS_2];
Move EasyMove = MOVE_NONE;
Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
// Initialize
TT.new_search();
H.clear();
- init_ss_array(ss);
+ init_ss_array(ss, PLY_MAX_PLUS_2);
ValueByIteration[1] = rml.get_move_score(0);
+ p.reset_ply();
Iteration = 1;
// Is one move significantly better than others after initial scoring ?
// Step 5. Evaluate the position statically
// At root we do this only to get reference value for child nodes
if (!isCheck)
- ss->eval = evaluate(pos, ei, 0);
+ ss->eval = evaluate(pos, ei);
// Step 6. Razoring (omitted at root)
// Step 7. Static null move 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+1, -beta, -alpha, newDepth, 1, false, 0);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth);
}
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, 1, true, 0);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction);
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, 1, true, 0);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
// 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, 1, false, 0);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth);
}
}
// 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,
- int ply, bool allowNullmove, int threadID, Move excludedMove) {
+ Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
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());
+ assert(pos.ply() > 0 && pos.ply() < PLY_MAX);
+ assert(pos.thread() >= 0 && pos.thread() < TM.active_threads());
Move movesSearched[256];
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
bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
bool mateThreat = false;
int moveCount = 0;
+ int threadID = pos.thread();
+ int ply = pos.ply();
refinedValue = bestValue = value = -VALUE_INFINITE;
oldAlpha = alpha;
- if (depth < OnePly)
- return qsearch<PvNode>(pos, ss, alpha, beta, Depth(0), ply, threadID);
+ // Step 1. Initialize node and poll. Polling can abort search
+ TM.incrementNodeCounter(threadID);
+ ss->init(ply);
+ (ss + 2)->initKillers();
- // Step 1. Initialize node and poll
- // Polling can abort search.
- init_node(ss, ply, threadID);
+ if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
+ {
+ NodesSincePoll = 0;
+ poll();
+ }
// Step 2. Check for aborted search and immediate draw
if (AbortSearch || TM.thread_should_stop(threadID))
// 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);
ei.kingDanger[pos.side_to_move()] = tte->king_danger();
}
else
- ss->eval = evaluate(pos, ei, threadID);
+ ss->eval = evaluate(pos, ei);
refinedValue = refine_eval(tte, ss->eval, ply); // Enhance accuracy with TT value if possible
update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
// Step 6. Razoring (is omitted in PV nodes)
if ( !PvNode
+ && depth < RazorDepth
+ && !isCheck
&& refinedValue < beta - razor_margin(depth)
&& ttMove == MOVE_NONE
&& (ss-1)->currentMove != MOVE_NULL
- && depth < RazorDepth
- && !isCheck
&& !value_is_mate(beta)
&& !pos.has_pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
+ Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, Depth(0));
if (v < rbeta)
// Logically we should return (v + razor_margin(depth)), but
// surprisingly this did slightly weaker in tests.
// 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
&& !value_is_mate(beta)
- && ok_to_do_nullmove(pos)
- && refinedValue >= beta + futility_margin(depth, 0))
+ && pos.non_pawn_material(pos.side_to_move()))
return refinedValue - futility_margin(depth, 0);
// Step 8. Null move search with verification search (is omitted in PV nodes)
// 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
&& !value_is_mate(beta)
- && ok_to_do_nullmove(pos)
- && refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0))
+ && pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
R++;
pos.do_null_move(st);
+ (ss+1)->skipNullMove = true;
- nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly, ply+1, false, threadID);
-
+ nullValue = depth-R*OnePly < OnePly ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, Depth(0))
+ : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly);
+ (ss+1)->skipNullMove = false;
pos.undo_null_move();
if (nullValue >= beta)
if (nullValue >= value_mate_in(PLY_MAX))
nullValue = beta;
+ // Do zugzwang verification search at high depths
if (depth < 6 * OnePly)
return nullValue;
- // Do zugzwang verification search
- Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, ply, false, threadID);
+ ss->skipNullMove = true;
+ Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly);
+ ss->skipNullMove = false;
+
if (v >= beta)
return nullValue;
- } else {
+ }
+ else
+ {
// The null move failed low, which means that we may be faced with
// some kind of threat. If the previous move was reduced, check if
// the move that refuted the null move was somehow connected to the
&& (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
{
Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
- search<PvNode>(pos, ss, alpha, beta, d, ply, false, threadID);
+
+ ss->skipNullMove = true;
+ search<PvNode>(pos, ss, alpha, beta, d);
+ ss->skipNullMove = false;
+
ttMove = ss->pv[ply];
tte = TT.retrieve(posKey);
}
// Initialize a MovePicker object for the current position
MovePicker mp = MovePicker(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
CheckInfo ci(pos);
+ bool singularExtensionNode = depth >= SingularExtensionDepth[PvNode]
+ && tte && tte->move()
+ && !excludedMove // Do not allow recursive singular extension search
+ && is_lower_bound(tte->type())
+ && tte->depth() >= depth - 3 * OnePly;
// Step 10. Loop through moves
// Loop through all legal moves until no moves remain or a beta cutoff occurs
// 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 >= SingularExtensionDepth[PvNode]
- && tte
+ if ( singularExtensionNode
&& move == tte->move()
- && !excludedMove // Do not allow recursive singular extension search
- && ext < OnePly
- && is_lower_bound(tte->type())
- && tte->depth() >= depth - 3 * OnePly)
+ && ext < OnePly)
{
Value ttValue = value_from_tt(tte->value(), ply);
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
Value b = ttValue - SingularExtensionMargin;
- Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply, false, threadID, move);
+ ss->excludedMove = move;
+ ss->skipNullMove = true;
+ Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2);
+ ss->skipNullMove = false;
+ ss->excludedMove = MOVE_NONE;
if (v < ttValue - SingularExtensionMargin)
ext = OnePly;
// Step 12. Futility pruning (is omitted in PV nodes)
if ( !PvNode
+ && !captureOrPromotion
&& !isCheck
&& !dangerous
- && !captureOrPromotion
- && !move_is_castle(move)
- && move != ttMove)
+ && move != ttMove
+ && !move_is_castle(move))
{
// Move count based pruning
if ( moveCount >= futility_move_count(depth)
- && ok_to_prune(pos, move, ss->threatMove)
+ && !(ss->threatMove && connected_threat(pos, move, ss->threatMove))
&& bestValue > value_mated_in(PLY_MAX))
continue;
// 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+1, -beta, -alpha, newDepth, ply+1, false, threadID);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0))
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
else
{
// Step 14. Reduced depth search
bool doFullDepthSearch = true;
if ( depth >= 3 * OnePly
- && !dangerous
&& !captureOrPromotion
+ && !dangerous
&& !move_is_castle(move)
&& !move_is_killer(move, ss))
{
ss->reduction = reduction<PvNode>(depth, moveCount);
if (ss->reduction)
{
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1, true, threadID);
+ Depth d = newDepth - ss->reduction;
+ value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0))
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
+
doFullDepthSearch = (value > alpha);
}
// 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 = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1, true, threadID);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction);
doFullDepthSearch = (value > alpha);
}
+ ss->reduction = Depth(0); // Restore original reduction
}
// Step 15. Full depth search
if (doFullDepthSearch)
{
- ss->reduction = Depth(0);
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1, true, threadID);
+ value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0))
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
// 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+1, -beta, -alpha, newDepth, ply+1, false, threadID);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0))
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
}
}
}
// Step 18. Check for split
- if ( TM.active_threads() > 1
+ if ( depth >= MinimumSplitDepth
+ && TM.active_threads() > 1
&& bestValue < beta
- && depth >= MinimumSplitDepth
- && Iteration <= 99
&& TM.available_thread_exists(threadID)
&& !AbortSearch
- && !TM.thread_should_stop(threadID))
- TM.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
- mateThreat, &moveCount, &mp, threadID, PvNode);
+ && !TM.thread_should_stop(threadID)
+ && Iteration <= 99)
+ TM.split<FakeSplit>(pos, ss, &alpha, beta, &bestValue, depth,
+ mateThreat, &moveCount, &mp, PvNode);
}
// Step 19. Check for mate and stalemate
// less than OnePly).
template <NodeType PvNode>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta,
- Depth depth, int ply, int threadID) {
+ Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
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());
+ assert(pos.ply() > 0 && pos.ply() < PLY_MAX);
+ assert(pos.thread() >= 0 && pos.thread() < TM.active_threads());
EvalInfo ei;
StateInfo st;
Move ttMove, move;
- Value staticValue, bestValue, value, futilityBase, futilityValue;
+ Value staticValue, bestValue, value, futilityBase;
bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
const TTEntry* tte = NULL;
int moveCount = 0;
+ int ply = pos.ply();
Value oldAlpha = alpha;
+ Value futilityValue = VALUE_INFINITE;
- // Initialize, and make an early exit in case of an aborted search,
- // an instant draw, maximum ply reached, etc.
- init_node(ss, ply, threadID);
-
- // After init_node() that calls poll()
- if (AbortSearch || TM.thread_should_stop(threadID))
- return Value(0);
+ TM.incrementNodeCounter(pos.thread());
+ ss->init(ply);
+ // Check for an instant draw or maximum ply reached
if (pos.is_draw() || ply >= PLY_MAX - 1)
return VALUE_DRAW;
ei.kingDanger[pos.side_to_move()] = tte->king_danger();
}
else
- staticValue = evaluate(pos, ei, threadID);
+ staticValue = evaluate(pos, ei);
if (!isCheck)
{
return bestValue;
}
- if (bestValue > alpha)
+ if (PvNode && bestValue > alpha)
alpha = bestValue;
// If we are near beta then try to get a cutoff pushing checks a bit further
&& !move_is_promotion(move)
&& !pos.move_is_passed_pawn_push(move))
{
+ // Can only decrease from previous move because of
+ // MVV ordering so we don't need to recheck.
+ if (futilityValue < alpha)
+ continue;
+
futilityValue = futilityBase
+ pos.endgame_value_of_piece_on(move_to(move))
+ (move_is_ep(move) ? PawnValueEndgame : Value(0));
// Make and search the move
pos.do_move(move, st, ci, moveIsCheck);
- value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-OnePly, ply+1, threadID);
+ value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-OnePly);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
int moveCount;
value = -VALUE_INFINITE;
- Position pos(*sp->pos);
+ Position pos(*sp->pos, threadID);
CheckInfo ci(pos);
+ int ply = pos.ply();
SearchStack* ss = sp->sstack[threadID] + 1;
isCheck = pos.is_check();
// Step 12. Futility pruning (is omitted in PV nodes)
if ( !PvNode
+ && !captureOrPromotion
&& !isCheck
&& !dangerous
- && !captureOrPromotion
&& !move_is_castle(move))
{
// Move count based pruning
if ( moveCount >= futility_move_count(sp->depth)
- && ok_to_prune(pos, move, ss->threatMove)
+ && !(ss->threatMove && connected_threat(pos, move, ss->threatMove))
&& sp->bestValue > value_mated_in(PLY_MAX))
{
lock_grab(&(sp->lock));
// 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, sp->ply+1, true, threadID);
+ Depth d = newDepth - ss->reduction;
+ value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0))
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d);
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, sp->ply+1, true, threadID);
+ value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction);
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, sp->ply+1, true, threadID);
+ value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0))
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth);
+ // 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, sp->ply+1, false, threadID);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -sp->beta, -sp->alpha, Depth(0))
+ : - search<PV>(pos, ss+1, -sp->beta, -sp->alpha, newDepth);
}
// Step 16. Undo move
if (PvNode && value < sp->beta) // This guarantees that always: sp->alpha < sp->beta
sp->alpha = value;
- sp_update_pv(sp->parentSstack, ss, sp->ply);
+ sp_update_pv(sp->parentSstack, ss, ply);
}
}
}
lock_release(&(sp->lock));
}
- // init_node() is called at the beginning of all the search functions
- // (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.
-
- void init_node(SearchStack* ss, int ply, int threadID) {
-
- assert(ply >= 0 && ply < PLY_MAX);
- assert(threadID >= 0 && threadID < TM.active_threads());
-
- TM.incrementNodeCounter(threadID);
-
- if (threadID == 0)
- {
- NodesSincePoll++;
- if (NodesSincePoll >= NodesBetweenPolls)
- {
- poll();
- NodesSincePoll = 0;
- }
- }
- ss->init(ply);
- (ss + 2)->initKillers();
- }
-
// update_pv() is called whenever a search returns a value > alpha.
// It updates the PV in the SearchStack object corresponding to the
// current node.
}
- // ok_to_do_nullmove() looks at the current position and decides whether
- // doing a 'null move' should be allowed. In order to avoid zugzwang
- // problems, null moves are not allowed when the side to move has very
- // little material left. Currently, the test is a bit too simple: Null
- // moves are avoided only when the side to move has only pawns left.
- // It's probably a good idea to avoid null moves in at least some more
- // complicated endgames, e.g. KQ vs KR. FIXME
-
- bool ok_to_do_nullmove(const Position& pos) {
-
- return pos.non_pawn_material(pos.side_to_move()) != Value(0);
- }
-
+ // connected_threat() tests whether it is safe to forward prune a move or if
+ // is somehow coonected to the threat move returned by null search.
- // ok_to_prune() tests whether it is safe to forward prune a move. Only
- // non-tactical moves late in the move list close to the leaves are
- // candidates for pruning.
-
- bool ok_to_prune(const Position& pos, Move m, Move threat) {
+ bool connected_threat(const Position& pos, Move m, Move threat) {
assert(move_is_ok(m));
- assert(threat == MOVE_NONE || move_is_ok(threat));
+ assert(threat && move_is_ok(threat));
assert(!pos.move_is_check(m));
assert(!pos.move_is_capture_or_promotion(m));
assert(!pos.move_is_passed_pawn_push(m));
Square mfrom, mto, tfrom, tto;
- // Prune if there isn't any threat move
- if (threat == MOVE_NONE)
- return true;
-
mfrom = move_from(m);
mto = move_to(m);
tfrom = move_from(threat);
// Case 1: Don't prune moves which move the threatened piece
if (mfrom == tto)
- return false;
+ return true;
// Case 2: If the threatened piece has value less than or equal to the
// value of the threatening piece, don't prune move which defend it.
&& ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
|| pos.type_of_piece_on(tfrom) == KING)
&& pos.move_attacks_square(m, tto))
- return false;
+ return true;
// Case 3: If the moving piece in the threatened move is a slider, don't
// prune safe moves which block its ray.
if ( piece_is_slider(pos.piece_on(tfrom))
&& bit_is_set(squares_between(tfrom, tto), mto)
&& pos.see_sign(m) >= 0)
- return false;
+ return true;
- return true;
+ return false;
}
}
- // init_ss_array() does a fast reset of the first entries of a SearchStack array
+ // init_ss_array() does a fast reset of the first entries of a SearchStack
+ // array and of all the excludedMove and skipNullMove entries.
- void init_ss_array(SearchStack* ss) {
+ void init_ss_array(SearchStack* ss, int size) {
- for (int i = 0; i < 3; i++, ss++)
+ for (int i = 0; i < size; i++, ss++)
{
- ss->init(i);
- ss->initKillers();
+ ss->excludedMove = MOVE_NONE;
+ ss->skipNullMove = false;
+
+ if (i < 3)
+ {
+ ss->init(i);
+ ss->initKillers();
+ }
}
}
// Initialize SplitPointStack locks
for (i = 0; i < MAX_THREADS; i++)
for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++)
- {
- SplitPointStack[i][j].parent = NULL;
lock_init(&(SplitPointStack[i][j].lock), NULL);
- }
// Will be set just before program exits to properly end the threads
AllThreadsShouldExit = false;
// Wait for thread termination
for (int i = 1; i < MAX_THREADS; i++)
- while (threads[i].state != THREAD_TERMINATED);
+ while (threads[i].state != THREAD_TERMINATED) {}
// Now we can safely destroy the locks
for (int i = 0; i < MAX_THREADS; i++)
// split() returns.
template <bool Fake>
- void ThreadsManager::split(const Position& p, SearchStack* ss, int ply, Value* alpha,
- const Value beta, Value* bestValue, Depth depth, bool mateThreat,
- int* moveCount, MovePicker* mp, int master, bool pvNode) {
+ void ThreadsManager::split(const Position& p, SearchStack* ss, Value* alpha, const Value beta,
+ Value* bestValue, Depth depth, bool mateThreat, int* moveCount,
+ MovePicker* mp, bool pvNode) {
assert(p.is_ok());
- assert(ply > 0 && ply < PLY_MAX);
assert(*bestValue >= -VALUE_INFINITE);
assert(*bestValue <= *alpha);
assert(*alpha < beta);
assert(beta <= VALUE_INFINITE);
assert(depth > Depth(0));
- assert(master >= 0 && master < ActiveThreads);
+ assert(p.thread() >= 0 && p.thread() < ActiveThreads);
assert(ActiveThreads > 1);
+ int master = p.thread();
+
lock_grab(&MPLock);
// If no other thread is available to help us, or if we have too many
// Initialize the split point object
splitPoint->parent = threads[master].splitPoint;
splitPoint->stopRequest = false;
- splitPoint->ply = ply;
splitPoint->depth = depth;
splitPoint->mateThreat = mateThreat;
splitPoint->alpha = *alpha;
continue;
// Find a quick score for the move
- init_ss_array(ss);
+ init_ss_array(ss, PLY_MAX_PLUS_2);
pos.do_move(cur->move, st);
moves[count].move = cur->move;
- moves[count].score = -qsearch<PV>(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
+ moves[count].score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0));
moves[count].pv[0] = cur->move;
moves[count].pv[1] = MOVE_NONE;
pos.undo_move(cur->move);