Retire ok_to_do_nullmove()
Has been remained the same from ages also with the FIXME. Retire for now and rearrange the conditions order for maximum performance. Also a small touch at null zugzwang verification. No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>sf_2.3.1_base
Marco Costalba
parent
7903495b0a
commit
50e094ef8d
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@ -301,7 +301,6 @@ namespace {
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bool connected_moves(const Position& pos, Move m1, Move m2);
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bool value_is_mate(Value value);
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bool move_is_killer(Move m, SearchStack* ss);
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bool ok_to_do_nullmove(const Position& pos);
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bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
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bool connected_threat(const Position& pos, Move m, Move threat);
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Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
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@ -1125,11 +1124,11 @@ namespace {
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// Step 6. Razoring (is omitted in PV nodes)
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if ( !PvNode
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&& depth < RazorDepth
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&& !isCheck
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&& refinedValue < beta - razor_margin(depth)
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&& ttMove == MOVE_NONE
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&& (ss-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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@ -1147,10 +1146,10 @@ namespace {
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if ( !PvNode
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&& allowNullmove
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&& depth < RazorDepth
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&& refinedValue >= beta + futility_margin(depth, 0)
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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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&& pos.non_pawn_material(pos.side_to_move()))
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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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@ -1160,10 +1159,10 @@ namespace {
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if ( !PvNode
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&& allowNullmove
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&& depth > OnePly
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&& refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0)
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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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&& pos.non_pawn_material(pos.side_to_move()))
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{
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ss->currentMove = MOVE_NULL;
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@ -1186,14 +1185,13 @@ namespace {
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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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// Do zugzwang verification search at high depths
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if ( depth < 6 * OnePly
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|| search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, false, threadID) >= beta)
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return nullValue;
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// Do zugzwang verification search
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Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, false, threadID);
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if (v >= beta)
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return nullValue;
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} else {
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}
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else
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{
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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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@ -1279,11 +1277,11 @@ namespace {
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// Step 12. Futility pruning (is omitted in PV nodes)
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if ( !PvNode
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&& !captureOrPromotion
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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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&& move != ttMove
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&& !move_is_castle(move))
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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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@ -1321,8 +1319,8 @@ namespace {
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bool doFullDepthSearch = true;
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if ( depth >= 3 * OnePly
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&& !dangerous
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&& !captureOrPromotion
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&& !dangerous
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&& !move_is_castle(move)
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&& !move_is_killer(move, ss))
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{
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@ -1387,13 +1385,13 @@ namespace {
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}
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// Step 18. Check for split
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if ( TM.active_threads() > 1
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if ( depth >= MinimumSplitDepth
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&& TM.active_threads() > 1
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&& bestValue < beta
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&& depth >= MinimumSplitDepth
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&& Iteration <= 99
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&& TM.available_thread_exists(threadID)
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&& !AbortSearch
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&& !TM.thread_should_stop(threadID))
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&& !TM.thread_should_stop(threadID)
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&& Iteration <= 99)
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TM.split<FakeSplit>(pos, ss, &alpha, beta, &bestValue, depth,
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mateThreat, &moveCount, &mp, threadID, PvNode);
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}
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@ -1965,20 +1963,6 @@ namespace {
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}
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// ok_to_do_nullmove() looks at the current position and decides whether
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// doing a 'null move' should be allowed. In order to avoid zugzwang
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// problems, null moves are not allowed when the side to move has very
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// little material left. Currently, the test is a bit too simple: Null
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// moves are avoided only when the side to move has only pawns left.
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// It's probably a good idea to avoid null moves in at least some more
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// complicated endgames, e.g. KQ vs KR. FIXME
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bool ok_to_do_nullmove(const Position& pos) {
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return pos.non_pawn_material(pos.side_to_move()) != Value(0);
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}
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// connected_threat() tests whether it is safe to forward prune a move or if
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// is somehow coonected to the threat move returned by null search.
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