// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
- return d > 14 ? 73 : 6 * d * d + 229 * d - 215;
+ return std::min((6 * d + 229) * d - 215 , 2000);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
ttCapture, singularQuietLMR, noLMRExtension;
Piece movedPiece;
- int moveCount, captureCount, quietCount;
+ int moveCount, captureCount, quietCount, bestMoveCount;
// Step 1. Initialize node
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
- moveCount = captureCount = quietCount = ss->moveCount = 0;
+ moveCount = bestMoveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
else
{
// In case of null move search use previous static eval with a different sign
- // and addition of two tempos
if ((ss-1)->currentMove != MOVE_NULL)
ss->staticEval = eval = evaluate(pos);
else
else if (singularBeta >= beta)
return singularBeta;
- // If the eval of ttMove is greater than beta we try also if there is another
- // move that pushes it over beta, if so the position also has probably multiple
- // moves giving fail highs. We will then reduce the ttMove (negative extension).
+ // If the eval of ttMove is greater than beta, we reduce it (negative extension)
else if (ttValue >= beta)
- {
- ss->excludedMove = move;
- value = search<NonPV>(pos, ss, beta - 1, beta, (depth + 3) / 2, cutNode);
- ss->excludedMove = MOVE_NONE;
-
- if (value >= beta)
- extension = -2;
- }
+ extension = -2;
}
// Capture extensions for PvNodes and cutNodes
{
Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
- if (PvNode)
+ // Decrease reduction if on the PV (~2 Elo)
+ if ( PvNode
+ && bestMoveCount <= 3)
r--;
// Decrease reduction if the ttHit running average is large (~0 Elo)
update_pv(ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha! Always alpha < beta
+ {
alpha = value;
+ bestMoveCount++;
+ }
else
{
assert(value >= beta); // Fail high
}
else
// In case of null move search use previous static eval with a different sign
- // and addition of two tempos
ss->staticEval = bestValue =
(ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
: -(ss-1)->staticEval;
PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
bonus1 = stat_bonus(depth + 1);
- bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
- : std::min(bonus1, stat_bonus(depth)); // smaller bonus
+ bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
+ : stat_bonus(depth); // smaller bonus
if (!pos.capture_or_promotion(bestMove))
{