void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
- Reductions[i] = int(21.3 * std::log(i + 0.25 * std::log(i)));
+ Reductions[i] = int(21.9 * std::log(i));
}
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
ss->staticEval = eval = -(ss-1)->staticEval;
// Save static evaluation into transposition table
+ if(!excludedMove)
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
// Step 7. Futility pruning: child node (~50 Elo)
if ( !PvNode
- && depth < 9
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
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.
continue;
// Futility pruning: parent node (~5 Elo)
- if ( lmrDepth < 7
- && !ss->inCheck
+ if ( !ss->inCheck
&& ss->staticEval + 174 + 157 * lmrDepth <= alpha
&& (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
{
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++;
r--;
// Increase reduction for cut nodes (~3 Elo)
- if (cutNode)
- r += 1 + !captureOrPromotion;
+ if (cutNode && move != ss->killers[0])
+ r += 2;
if (!captureOrPromotion)
{
// 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);
{
assert(is_ok(move));
+ // Check for legality
+ if (!pos.legal(move))
+ continue;
+
givesCheck = pos.gives_check(move);
captureOrPromotion = pos.capture_or_promotion(move);
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
- // Check for legality just before making the move
- if (!pos.legal(move))
- {
- moveCount--;
- continue;
- }
-
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
[captureOrPromotion]