// Step 8. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 22661
+ && (ss-1)->statScore < 24185
&& eval >= beta
&& eval >= ss->staticEval
&& ss->staticEval >= beta - 24 * depth - 34 * improving + 162 * ss->ttPv + 159
moves_loop: // When in check, search starts from here
+ ttCapture = ttMove && pos.capture_or_promotion(ttMove);
+
+ // Step 11. A small Probcut idea, when we are in check
+ probCutBeta = beta + 400;
+ if ( ss->inCheck
+ && !PvNode
+ && depth >= 4
+ && ttCapture
+ && (tte->bound() & BOUND_LOWER)
+ && tte->depth() >= depth - 3
+ && ttValue >= probCutBeta
+ && abs(ttValue) <= VALUE_KNOWN_WIN
+ && abs(beta) <= VALUE_KNOWN_WIN
+ )
+ return probCutBeta;
+
+
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
nullptr , (ss-4)->continuationHistory,
nullptr , (ss-6)->continuationHistory };
value = bestValue;
singularQuietLMR = moveCountPruning = false;
- ttCapture = ttMove && pos.capture_or_promotion(ttMove);
// Mark this node as being searched
ThreadHolding th(thisThread, posKey, ss->ply);
- // Step 11. Loop through all pseudo-legal moves until no moves remain
+ // Step 12. Loop through all pseudo-legal moves until no moves remain
// or a beta cutoff occurs.
while ((move = mp.next_move(moveCountPruning)) != MOVE_NONE)
{
movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move);
- // Indicate PvNodes that will probably fail low if node was searched with non-PV search
+ // Indicate PvNodes that will probably fail low if node was searched with non-PV search
// at depth equal or greater to current depth and result of this search was far below alpha
- bool likelyFailLow = PvNode
- && ttMove
- && (tte->bound() & BOUND_UPPER)
- && ttValue < alpha + 200 + 100 * depth
+ bool likelyFailLow = PvNode
+ && ttMove
+ && (tte->bound() & BOUND_UPPER)
+ && ttValue < alpha + 200 + 100 * depth
&& tte->depth() >= depth;
// Calculate new depth for this move
newDepth = depth - 1;
- // Step 12. Pruning at shallow depth (~200 Elo)
+ // Step 13. Pruning at shallow depth (~200 Elo)
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
&& (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- + (*contHist[5])[movedPiece][to_sq(move)] / 3 < 26237)
+ + (*contHist[5])[movedPiece][to_sq(move)] / 3 < 28255)
continue;
// Prune moves with negative SEE (~20 Elo)
}
}
- // Step 13. Extensions (~75 Elo)
+ // Step 14. Extensions (~75 Elo)
// Singular extension search (~70 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
[movedPiece]
[to_sq(move)];
- // Step 14. Make the move
+ // Step 15. Make the move
pos.do_move(move, st, givesCheck);
- // Step 15. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
+ // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
// re-searched at full depth.
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode
- || (!PvNode && !formerPv && captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 4506)
+ || (!PvNode && !formerPv && captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 3678)
|| thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024))
{
Depth r = reduction(improving, depth, moveCount);
if (th.marked())
r++;
- // Decrease reduction if position is or has been on the PV
- // and node is not likely to fail low (~10 Elo)
+ // Decrease reduction if position is or has been on the PV
+ // and node is not likely to fail low. (~10 Elo)
if (ss->ttPv && !likelyFailLow)
r -= 2;
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- - 5337;
+ - 4741;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= -89 && (ss-1)->statScore < -116)
// use 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)] - 4341) / 16384;
+ + (*contHist[0])[movedPiece][to_sq(move)] - 3833) / 16384;
else
- r -= ss->statScore / 14382;
+ r -= ss->statScore / 14790;
}
Depth d = std::clamp(newDepth - r, 1, newDepth);
didLMR = false;
}
- // Step 16. Full depth search when LMR is skipped or fails high
+ // Step 17. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
{
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
std::min(maxNextDepth, newDepth), false);
}
- // Step 17. Undo move
+ // Step 18. Undo move
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Step 18. Check for a new best move
+ // Step 19. Check for a new best move
// Finished searching the move. If a stop occurred, the return value of
// the search cannot be trusted, and we return immediately without
// updating best move, PV and TT.
return VALUE_DRAW;
*/
- // Step 19. Check for mate and stalemate
+ // Step 20. Check for mate and stalemate
// All legal moves have been searched and if there are no legal moves, it
// must be a mate or a stalemate. If we are in a singular extension search then
// return a fail low score.