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https://github.com/sockspls/badfish
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Unite search_pv() and search()
A lot of redundant code removed: -182 lines of code No functional and speed change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Joona Kiiski
Marco Costalba
parent
c0334c7bac
commit
b075d8ca53
1 changed files with 206 additions and 388 deletions
590
src/search.cpp
590
src/search.cpp
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@ -194,8 +194,7 @@ namespace {
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Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
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// Minimum depth for use of singular extension
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const Depth SingularExtensionDepthAtPVNodes = 6 * OnePly;
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const Depth SingularExtensionDepthAtNonPVNodes = 8 * OnePly;
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const Depth SingularExtensionDepth[2] = { 8 * OnePly /* non-PV */, 6 * OnePly /* PV */};
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// If the TT move is at least SingularExtensionMargin better then the
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// remaining ones we will extend it.
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@ -280,8 +279,10 @@ namespace {
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Value id_loop(const Position& pos, Move searchMoves[]);
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Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
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Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
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Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
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template <bool PvNode>
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Value search(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
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Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
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void sp_search(SplitPoint* sp, int threadID);
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void sp_search_pv(SplitPoint* sp, int threadID);
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@ -869,7 +870,7 @@ namespace {
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alpha = -VALUE_INFINITE;
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// Full depth PV search, done on first move or after a fail high
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value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
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value = -search<true>(pos, ss, -beta, -alpha, newDepth, 1, false, 0);
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}
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else
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{
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@ -886,7 +887,7 @@ namespace {
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if (ss[0].reduction)
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{
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// Reduced depth non-pv search using alpha as upperbound
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value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
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value = -search<false>(pos, ss, -(alpha+1), -alpha, newDepth-ss[0].reduction, 1, true, 0);
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doFullDepthSearch = (value > alpha);
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}
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}
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@ -896,12 +897,12 @@ namespace {
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{
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// Full depth non-pv search using alpha as upperbound
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ss[0].reduction = Depth(0);
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value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
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value = -search<false>(pos, ss, -(alpha+1), -alpha, newDepth, 1, true, 0);
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// If we are above alpha then research at same depth but as PV
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// to get a correct score or eventually a fail high above beta.
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if (value > alpha)
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value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
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value = -search<true>(pos, ss, -beta, -alpha, newDepth, 1, false, 0);
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}
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}
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@ -1023,8 +1024,10 @@ namespace {
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// search_pv() is the main search function for PV nodes.
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Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta,
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Depth depth, int ply, int threadID) {
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template <bool PvNode>
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Value search(Position& pos, SearchStack ss[], Value alpha, Value beta,
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Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove) {
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assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
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assert(beta > alpha && beta <= VALUE_INFINITE);
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@ -1038,10 +1041,12 @@ namespace {
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Move ttMove, move;
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Depth ext, newDepth;
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Value bestValue, value, oldAlpha;
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Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific
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bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
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bool mateThreat = false;
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int moveCount = 0;
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bestValue = value = -VALUE_INFINITE;
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refinedValue = bestValue = value = -VALUE_INFINITE;
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oldAlpha = alpha;
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if (depth < OnePly)
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return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
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@ -1058,13 +1063,20 @@ namespace {
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return VALUE_DRAW;
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// Step 3. Mate distance pruning
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oldAlpha = alpha;
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alpha = Max(value_mated_in(ply), alpha);
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beta = Min(value_mate_in(ply+1), beta);
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if (alpha >= beta)
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return alpha;
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// Step 4. Transposition table lookup
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// We don't want the score of a partial search to overwrite a previous full search
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// TT value, so we use a different position key in case of an excluded move exists.
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Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
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tte = TT.retrieve(posKey);
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ttMove = (tte ? tte->move() : MOVE_NONE);
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// At PV nodes, we don't use the TT for pruning, but only for move ordering.
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// This is to avoid problems in the following areas:
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//
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@ -1072,57 +1084,173 @@ namespace {
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// * Fifty move rule detection
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// * Searching for a mate
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// * Printing of full PV line
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tte = TT.retrieve(pos.get_key());
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ttMove = (tte ? tte->move() : MOVE_NONE);
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if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
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{
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// Refresh tte entry to avoid aging
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TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove);
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ss[ply].currentMove = ttMove; // Can be MOVE_NONE
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return value_from_tt(tte->value(), ply);
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}
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// Step 5. Evaluate the position statically
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// At PV nodes we do this only to update gain statistics
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isCheck = pos.is_check();
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if (!isCheck)
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{
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if (!PvNode && tte && (tte->type() & VALUE_TYPE_EVAL))
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ss[ply].eval = value_from_tt(tte->value(), ply);
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else
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ss[ply].eval = evaluate(pos, ei, threadID);
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refinedValue = refine_eval(tte, ss[ply].eval, ply); // Enhance accuracy with TT value if possible
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update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
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}
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// Step 6. Razoring (is omitted in PV nodes)
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// Step 7. Static null move pruning (is omitted in PV nodes)
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// Step 8. Null move search with verification search (is omitted in PV nodes)
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// Step 9. Internal iterative deepening
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if ( depth >= IIDDepthAtPVNodes
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&& ttMove == MOVE_NONE)
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if ( !PvNode
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&& refinedValue < beta - razor_margin(depth)
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&& ttMove == MOVE_NONE
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&& ss[ply - 1].currentMove != MOVE_NULL
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&& depth < RazorDepth
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&& !isCheck
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&& !value_is_mate(beta)
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&& !pos.has_pawn_on_7th(pos.side_to_move()))
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{
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search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
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ttMove = ss[ply].pv[ply];
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tte = TT.retrieve(pos.get_key());
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Value rbeta = beta - razor_margin(depth);
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Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
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if (v < rbeta)
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// Logically we should return (v + razor_margin(depth)), but
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// surprisingly this did slightly weaker in tests.
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return v;
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}
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// Initialize a MovePicker object for the current position
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// Step 7. Static null move pruning (is omitted in PV nodes)
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// We're betting that the opponent doesn't have a move that will reduce
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// the score by more than futility_margin(depth) if we do a null move.
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if ( !PvNode
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&& allowNullmove
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&& depth < RazorDepth
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&& !isCheck
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&& !value_is_mate(beta)
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&& ok_to_do_nullmove(pos)
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&& refinedValue >= beta + futility_margin(depth, 0))
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return refinedValue - futility_margin(depth, 0);
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// Step 8. Null move search with verification search (is omitted in PV nodes)
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// When we jump directly to qsearch() we do a null move only if static value is
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// at least beta. Otherwise we do a null move if static value is not more than
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// NullMoveMargin under beta.
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if ( !PvNode
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&& allowNullmove
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&& depth > OnePly
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&& !isCheck
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&& !value_is_mate(beta)
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&& ok_to_do_nullmove(pos)
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&& refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0))
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{
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ss[ply].currentMove = MOVE_NULL;
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// Null move dynamic reduction based on depth
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int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0);
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// Null move dynamic reduction based on value
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if (refinedValue - beta > PawnValueMidgame)
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R++;
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pos.do_null_move(st);
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nullValue = -search<false>(pos, ss, -beta, -alpha, depth-R*OnePly, ply+1, false, threadID);
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pos.undo_null_move();
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if (nullValue >= beta)
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{
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// Do not return unproven mate scores
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if (nullValue >= value_mate_in(PLY_MAX))
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nullValue = beta;
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if (depth < 6 * OnePly)
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return nullValue;
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// Do zugzwang verification search
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Value v = search<false>(pos, ss, alpha, beta, depth-5*OnePly, ply, false, threadID);
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if (v >= beta)
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return nullValue;
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} else {
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// The null move failed low, which means that we may be faced with
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// some kind of threat. If the previous move was reduced, check if
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// the move that refuted the null move was somehow connected to the
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// move which was reduced. If a connection is found, return a fail
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// low score (which will cause the reduced move to fail high in the
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// parent node, which will trigger a re-search with full depth).
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if (nullValue == value_mated_in(ply + 2))
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mateThreat = true;
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ss[ply].threatMove = ss[ply + 1].currentMove;
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if ( depth < ThreatDepth
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&& ss[ply - 1].reduction
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&& connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
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return beta - 1;
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}
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}
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// Step 9. Internal iterative deepening
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// We have different rules for PV nodes and non-pv nodes
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if ( PvNode
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&& depth >= IIDDepthAtPVNodes
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&& ttMove == MOVE_NONE)
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{
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search<true>(pos, ss, alpha, beta, depth-2*OnePly, ply, false, threadID);
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ttMove = ss[ply].pv[ply];
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tte = TT.retrieve(posKey);
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}
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if ( !PvNode
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&& depth >= IIDDepthAtNonPVNodes
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&& ttMove == MOVE_NONE
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&& !isCheck
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&& ss[ply].eval >= beta - IIDMargin)
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{
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search<false>(pos, ss, alpha, beta, depth/2, ply, false, threadID);
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ttMove = ss[ply].pv[ply];
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tte = TT.retrieve(posKey);
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}
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// Expensive mate threat detection (only for PV nodes)
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if (PvNode)
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mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
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MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
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// Initialize a MovePicker object for the current position
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MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], (PvNode ? -VALUE_INFINITE : beta));
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CheckInfo ci(pos);
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// Step 10. Loop through moves
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// Loop through all legal moves until no moves remain or a beta cutoff occurs
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while ( alpha < beta
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while ( bestValue < beta
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&& (move = mp.get_next_move()) != MOVE_NONE
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&& !TM.thread_should_stop(threadID))
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{
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assert(move_is_ok(move));
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if (move == excludedMove)
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continue;
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singleEvasion = (isCheck && mp.number_of_evasions() == 1);
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moveIsCheck = pos.move_is_check(move, ci);
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captureOrPromotion = pos.move_is_capture_or_promotion(move);
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// Step 11. Decide the new search depth
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ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
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ext = extension(pos, move, PvNode, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
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// Singular extension search. We extend the TT move if its value is much better than
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// its siblings. To verify this we do a reduced search on all the other moves but the
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// ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
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if ( depth >= SingularExtensionDepthAtPVNodes
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if ( depth >= SingularExtensionDepth[PvNode]
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&& tte
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&& move == tte->move()
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&& !excludedMove // Do not allow recursive singular extension search
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&& ext < OnePly
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&& is_lower_bound(tte->type())
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&& tte->depth() >= depth - 3 * OnePly)
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@ -1131,7 +1259,7 @@ namespace {
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if (abs(ttValue) < VALUE_KNOWN_WIN)
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{
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Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
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Value excValue = search<false>(pos, ss, ttValue - SingularExtensionMargin - 1, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
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if (excValue < ttValue - SingularExtensionMargin)
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ext = OnePly;
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@ -1144,14 +1272,39 @@ namespace {
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movesSearched[moveCount++] = ss[ply].currentMove = move;
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// Step 12. Futility pruning (is omitted in PV nodes)
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if ( !PvNode
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&& !isCheck
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&& !dangerous
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&& !captureOrPromotion
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&& !move_is_castle(move)
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&& move != ttMove)
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{
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// Move count based pruning
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if ( moveCount >= futility_move_count(depth)
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&& ok_to_prune(pos, move, ss[ply].threatMove)
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&& bestValue > value_mated_in(PLY_MAX))
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continue;
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// Value based pruning
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Depth predictedDepth = newDepth - nonpv_reduction(depth, moveCount); // We illogically ignore reduction condition depth >= 3*OnePly
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futilityValueScaled = ss[ply].eval + futility_margin(predictedDepth, moveCount)
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+ H.gain(pos.piece_on(move_from(move)), move_to(move));
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if (futilityValueScaled < beta)
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{
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if (futilityValueScaled > bestValue)
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bestValue = futilityValueScaled;
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continue;
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}
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}
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// Step 13. Make the move
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pos.do_move(move, st, ci, moveIsCheck);
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// Step extra. pv search (only in PV nodes)
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// The first move in list is the expected PV
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if (moveCount == 1)
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value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
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if (PvNode && moveCount == 1)
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value = -search<true>(pos, ss, -beta, -alpha, newDepth, ply+1, false, threadID);
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else
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{
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// Step 14. Reduced search
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@ -1164,10 +1317,10 @@ namespace {
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&& !move_is_castle(move)
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&& !move_is_killer(move, ss[ply]))
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{
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ss[ply].reduction = pv_reduction(depth, moveCount);
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ss[ply].reduction = (PvNode ? pv_reduction(depth, moveCount) : nonpv_reduction(depth, moveCount));
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if (ss[ply].reduction)
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{
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value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
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value = -search<false>(pos, ss, -(alpha+1), -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
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doFullDepthSearch = (value > alpha);
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}
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}
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@ -1176,11 +1329,11 @@ namespace {
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if (doFullDepthSearch)
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{
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ss[ply].reduction = Depth(0);
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value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
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value = -search<false>(pos, ss, -(alpha+1), -alpha, newDepth, ply+1, true, threadID);
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// Step extra. pv search (only in PV nodes)
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if (value > alpha && value < beta)
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value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
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if (PvNode && value > alpha && value < beta)
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value = -search<true>(pos, ss, -beta, -alpha, newDepth, ply+1, false, threadID);
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}
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}
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@ -1211,342 +1364,7 @@ namespace {
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&& !AbortSearch
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&& !TM.thread_should_stop(threadID)
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&& TM.split(pos, ss, ply, &alpha, beta, &bestValue,
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depth, mateThreat, &moveCount, &mp, threadID, true))
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break;
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}
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// Step 19. Check for mate and stalemate
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// All legal moves have been searched and if there were
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// no legal moves, it must be mate or stalemate.
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if (moveCount == 0)
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return (isCheck ? value_mated_in(ply) : VALUE_DRAW);
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// Step 20. Update tables
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// If the search is not aborted, update the transposition table,
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// history counters, and killer moves.
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if (AbortSearch || TM.thread_should_stop(threadID))
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return bestValue;
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if (bestValue <= oldAlpha)
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TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
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else if (bestValue >= beta)
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{
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TM.incrementBetaCounter(pos.side_to_move(), depth, threadID);
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move = ss[ply].pv[ply];
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if (!pos.move_is_capture_or_promotion(move))
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{
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update_history(pos, move, depth, movesSearched, moveCount);
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update_killers(move, ss[ply]);
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}
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TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move);
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}
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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
|
||||
// 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();
|
||||
|
||||
tte = TT.retrieve(posKey);
|
||||
ttMove = (tte ? tte->move() : MOVE_NONE);
|
||||
|
||||
if (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);
|
||||
|
||||
ss[ply].currentMove = ttMove; // Can be MOVE_NONE
|
||||
return value_from_tt(tte->value(), ply);
|
||||
}
|
||||
|
||||
// Step 5. Evaluate the position statically
|
||||
isCheck = pos.is_check();
|
||||
|
||||
if (!isCheck)
|
||||
{
|
||||
if (tte && (tte->type() & VALUE_TYPE_EVAL))
|
||||
ss[ply].eval = value_from_tt(tte->value(), ply);
|
||||
else
|
||||
ss[ply].eval = evaluate(pos, ei, threadID);
|
||||
|
||||
refinedValue = refine_eval(tte, ss[ply].eval, ply); // Enhance accuracy with TT value if possible
|
||||
update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
|
||||
}
|
||||
|
||||
// Step 6. Razoring
|
||||
if ( refinedValue < beta - razor_margin(depth)
|
||||
&& ttMove == MOVE_NONE
|
||||
&& ss[ply - 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(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
|
||||
// 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
|
||||
&& depth < RazorDepth
|
||||
&& !isCheck
|
||||
&& !value_is_mate(beta)
|
||||
&& ok_to_do_nullmove(pos)
|
||||
&& refinedValue >= beta + futility_margin(depth, 0))
|
||||
return refinedValue - futility_margin(depth, 0);
|
||||
|
||||
// Step 8. Null move search with verification search
|
||||
// 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
|
||||
&& depth > OnePly
|
||||
&& !isCheck
|
||||
&& !value_is_mate(beta)
|
||||
&& ok_to_do_nullmove(pos)
|
||||
&& refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0))
|
||||
{
|
||||
ss[ply].currentMove = MOVE_NULL;
|
||||
|
||||
// Null move dynamic reduction based on depth
|
||||
int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0);
|
||||
|
||||
// Null move dynamic reduction based on value
|
||||
if (refinedValue - beta > PawnValueMidgame)
|
||||
R++;
|
||||
|
||||
pos.do_null_move(st);
|
||||
|
||||
nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
|
||||
|
||||
pos.undo_null_move();
|
||||
|
||||
if (nullValue >= beta)
|
||||
{
|
||||
// Do not return unproven mate scores
|
||||
if (nullValue >= value_mate_in(PLY_MAX))
|
||||
nullValue = beta;
|
||||
|
||||
if (depth < 6 * OnePly)
|
||||
return nullValue;
|
||||
|
||||
// Do zugzwang verification search
|
||||
Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
|
||||
if (v >= beta)
|
||||
return nullValue;
|
||||
} 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
|
||||
// move which was reduced. If a connection is found, return a fail
|
||||
// low score (which will cause the reduced move to fail high in the
|
||||
// parent node, which will trigger a re-search with full depth).
|
||||
if (nullValue == value_mated_in(ply + 2))
|
||||
mateThreat = true;
|
||||
|
||||
ss[ply].threatMove = ss[ply + 1].currentMove;
|
||||
if ( depth < ThreatDepth
|
||||
&& ss[ply - 1].reduction
|
||||
&& connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
|
||||
return beta - 1;
|
||||
}
|
||||
}
|
||||
|
||||
// Step 9. Internal iterative deepening
|
||||
if ( depth >= IIDDepthAtNonPVNodes
|
||||
&& ttMove == MOVE_NONE
|
||||
&& !isCheck
|
||||
&& ss[ply].eval >= beta - IIDMargin)
|
||||
{
|
||||
search(pos, ss, beta, depth/2, ply, false, threadID);
|
||||
ttMove = ss[ply].pv[ply];
|
||||
tte = TT.retrieve(posKey);
|
||||
}
|
||||
|
||||
// Initialize a MovePicker object for the current position
|
||||
MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], beta);
|
||||
CheckInfo ci(pos);
|
||||
|
||||
// Step 10. Loop through moves
|
||||
// Loop through all legal moves until no moves remain or a beta cutoff occurs
|
||||
while ( bestValue < beta
|
||||
&& (move = mp.get_next_move()) != MOVE_NONE
|
||||
&& !TM.thread_should_stop(threadID))
|
||||
{
|
||||
assert(move_is_ok(move));
|
||||
|
||||
if (move == excludedMove)
|
||||
continue;
|
||||
|
||||
moveIsCheck = pos.move_is_check(move, ci);
|
||||
singleEvasion = (isCheck && mp.number_of_evasions() == 1);
|
||||
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);
|
||||
|
||||
// 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
|
||||
&& tte
|
||||
&& move == tte->move()
|
||||
&& !excludedMove // Do not allow recursive singular extension search
|
||||
&& 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
|
||||
if ( !isCheck
|
||||
&& !dangerous
|
||||
&& !captureOrPromotion
|
||||
&& !move_is_castle(move)
|
||||
&& move != ttMove)
|
||||
{
|
||||
// Move count based pruning
|
||||
if ( moveCount >= futility_move_count(depth)
|
||||
&& ok_to_prune(pos, move, ss[ply].threatMove)
|
||||
&& bestValue > value_mated_in(PLY_MAX))
|
||||
continue;
|
||||
|
||||
// Value based pruning
|
||||
Depth predictedDepth = newDepth - nonpv_reduction(depth, moveCount); // 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));
|
||||
|
||||
if (futilityValueScaled < beta)
|
||||
{
|
||||
if (futilityValueScaled > bestValue)
|
||||
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 ( depth >= 3*OnePly
|
||||
&& !dangerous
|
||||
&& !captureOrPromotion
|
||||
&& !move_is_castle(move)
|
||||
&& !move_is_killer(move, ss[ply]))
|
||||
{
|
||||
ss[ply].reduction = nonpv_reduction(depth, moveCount);
|
||||
if (ss[ply].reduction)
|
||||
{
|
||||
value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
|
||||
doFullDepthSearch = (value >= beta);
|
||||
}
|
||||
}
|
||||
|
||||
// Step 15. Full depth search
|
||||
if (doFullDepthSearch)
|
||||
{
|
||||
ss[ply].reduction = Depth(0);
|
||||
value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, 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 >= beta)
|
||||
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, NULL, beta, &bestValue,
|
||||
depth, mateThreat, &moveCount, &mp, threadID, false))
|
||||
depth, mateThreat, &moveCount, &mp, threadID, PvNode))
|
||||
break;
|
||||
}
|
||||
|
||||
|
|
@ -1555,7 +1373,7 @@ namespace {
|
|||
// 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,
|
||||
|
|
@ -1563,9 +1381,10 @@ namespace {
|
|||
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];
|
||||
|
|
@ -1575,8 +1394,9 @@ namespace {
|
|||
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);
|
||||
|
||||
|
|
@ -1868,7 +1688,7 @@ namespace {
|
|||
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);
|
||||
value = -search<false>(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));
|
||||
}
|
||||
}
|
||||
|
|
@ -1877,7 +1697,7 @@ namespace {
|
|||
if (doFullDepthSearch)
|
||||
{
|
||||
ss[sp->ply].reduction = Depth(0);
|
||||
value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
|
||||
value = -search<false>(pos, ss, -(sp->alpha+1), -(sp->alpha), newDepth, sp->ply+1, true, threadID);
|
||||
}
|
||||
|
||||
// Step 16. Undo move
|
||||
|
|
@ -1974,7 +1794,7 @@ namespace {
|
|||
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<false>(pos, ss, -(localAlpha+1), -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
|
||||
doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID));
|
||||
}
|
||||
}
|
||||
|
|
@ -1984,7 +1804,7 @@ namespace {
|
|||
{
|
||||
Value localAlpha = sp->alpha;
|
||||
ss[sp->ply].reduction = Depth(0);
|
||||
value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, true, threadID);
|
||||
value = -search<false>(pos, ss, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1, true, threadID);
|
||||
|
||||
if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID))
|
||||
{
|
||||
|
|
@ -1992,7 +1812,7 @@ namespace {
|
|||
// 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<true>(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, false, threadID);
|
||||
}
|
||||
}
|
||||
|
||||
|
|
@ -2032,7 +1852,7 @@ namespace {
|
|||
|
||||
|
||||
// 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.
|
||||
|
|
@ -2922,7 +2742,7 @@ namespace {
|
|||
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;
|
||||
|
|
@ -2977,12 +2797,10 @@ namespace {
|
|||
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;
|
||||
|
||||
*bestValue = splitPoint->bestValue;
|
||||
threads[master].activeSplitPoints--;
|
||||
threads[master].splitPoint = splitPoint->parent;
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue