probCutBeta = beta + 209 - 44 * improving;
- // Step 9. ProbCut (~10 Elo)
+ // Step 9. ProbCut (~4 Elo)
// If we have a good enough capture and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
&& ttValue != VALUE_NONE
&& ttValue < probCutBeta))
{
- // if ttMove is a capture and value from transposition table is good enough produce probCut
- // cutoff without digging into actual probCut search
- if ( ss->ttHit
- && tte->depth() >= depth - 3
- && ttValue != VALUE_NONE
- && ttValue >= probCutBeta
- && ttMove
- && pos.capture_or_promotion(ttMove))
- return probCutBeta;
-
assert(probCutBeta < VALUE_INFINITE);
MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory);
}
else
{
- // Countermoves based pruning (~20 Elo)
- if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
+ // Continuation history based pruning (~20 Elo)
+ if ( lmrDepth < 4
&& (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
&& (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
continue;
{
Depth r = reduction(improving, depth, moveCount);
- // Decrease reduction if the ttHit running average is large
+ // Decrease reduction if the ttHit running average is large (~0 Elo)
if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024)
r--;
// Decrease reduction if position is or has been on the PV
- // and node is not likely to fail low. (~10 Elo)
+ // and node is not likely to fail low. (~3 Elo)
if ( ss->ttPv
&& !likelyFailLow)
r -= 2;
r++;
// Increase reduction at root if failing high
- r += rootNode ? thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512 : 0;
+ if (rootNode)
+ r += thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512;
- // Increase reduction for cut nodes (~10 Elo)
+ // Increase reduction for cut nodes (~3 Elo)
if (cutNode)
r += 2;
+ (*contHist[3])[movedPiece][to_sq(move)]
- 4741;
- // Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
- if (ss->statScore >= -89 && (ss-1)->statScore < -116)
- r--;
-
- else if ((ss-1)->statScore >= -112 && ss->statScore < -100)
- r++;
-
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
- // If we are not in check use statScore, but if we are in check we use
- // the sum of main history and first continuation history with an offset.
- if (ss->inCheck)
- r -= (thisThread->mainHistory[us][from_to(move)]
- + (*contHist[0])[movedPiece][to_sq(move)] - 3833) / 16384;
- else
+ if (!ss->inCheck)
r -= ss->statScore / 14790;
}
[pos.moved_piece(move)]
[to_sq(move)];
- // CounterMove based pruning
+ // Continuation history based pruning
if ( !captureOrPromotion
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold