multiPV = std::min(multiPV, rootMoves.size());
ttHitAverage = TtHitAverageWindow * TtHitAverageResolution / 2;
- int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns
-
- // In analysis mode, adjust contempt in accordance with user preference
- if (Limits.infinite || Options["UCI_AnalyseMode"])
- ct = Options["Analysis Contempt"] == "Off" ? 0
- : Options["Analysis Contempt"] == "Both" ? ct
- : Options["Analysis Contempt"] == "White" && us == BLACK ? -ct
- : Options["Analysis Contempt"] == "Black" && us == WHITE ? -ct
- : ct;
-
- // Evaluation score is from the white point of view
- contempt = (us == WHITE ? make_score(ct, ct / 2)
- : -make_score(ct, ct / 2));
+ trend = SCORE_ZERO;
int searchAgainCounter = 0;
alpha = std::max(prev - delta,-VALUE_INFINITE);
beta = std::min(prev + delta, VALUE_INFINITE);
- // Adjust contempt based on root move's previousScore (dynamic contempt)
- int dct = ct + (113 - ct / 2) * prev / (abs(prev) + 147);
+ // Adjust trend based on root move's previousScore (dynamic contempt)
+ int tr = 113 * prev / (abs(prev) + 147);
- contempt = (us == WHITE ? make_score(dct, dct / 2)
- : -make_score(dct, dct / 2));
+ trend = (us == WHITE ? make_score(tr, tr / 2)
+ : -make_score(tr, tr / 2));
}
// Start with a small aspiration window and, in the case of a fail
assert(0 <= ss->ply && ss->ply < MAX_PLY);
- (ss+1)->ttPv = false;
+ (ss+1)->ttPv = false;
(ss+1)->excludedMove = bestMove = MOVE_NONE;
- (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
- Square prevSq = to_sq((ss-1)->currentMove);
+ (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+ ss->doubleExtensions = (ss-1)->doubleExtensions;
+ Square prevSq = to_sq((ss-1)->currentMove);
// Initialize statScore to zero for the grandchildren of the current position.
// So statScore is shared between all grandchildren and only the first grandchild
value = bestValue;
singularQuietLMR = moveCountPruning = false;
+ bool doubleExtension = false;
// Indicate PvNodes that will probably fail low if the node was searched
// at a depth equal or greater than the current depth, and the result of this search was a fail low.
{
extension = 1;
singularQuietLMR = !ttCapture;
- if (!PvNode && value < singularBeta - 93)
+
+ // Avoid search explosion by limiting the number of double extensions to at most 3
+ if ( !PvNode
+ && value < singularBeta - 93
+ && ss->doubleExtensions < 3)
+ {
extension = 2;
+ doubleExtension = true;
+ }
}
// Multi-cut pruning
// Add extension to new depth
newDepth += extension;
+ ss->doubleExtensions = (ss-1)->doubleExtensions + (extension == 2);
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
// Increase reduction at root and non-PV nodes when the best move does not change frequently
if ( (rootNode || !PvNode)
- && thisThread->rootDepth > 10
&& thisThread->bestMoveChanges <= 2)
r++;
// In general we want to cap the LMR depth search at newDepth. But if
// reductions are really negative and movecount is low, we allow this move
- // to be searched deeper than the first move.
- Depth d = std::clamp(newDepth - r, 1, newDepth + (r < -1 && moveCount <= 5));
+ // to be searched deeper than the first move, unless ttMove was extended by 2.
+ Depth d = std::clamp(newDepth - r, 1, newDepth + (r < -1 && moveCount <= 5 && !doubleExtension));
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
- // queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
+ // queen promotions, and other checks (only if depth >= DEPTH_QS_CHECKS)
// will be generated.
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
&thisThread->captureHistory,