killers[0].move = ss->killers[0];
killers[1].move = ss->killers[1];
Square prevSq = to_sq((ss-1)->currentMove);
- killers[2].move = cm[pos.piece_on(prevSq)][prevSq];
+ killers[2].move = cm[pos.piece_on(prevSq)][prevSq].first;
+ killers[3].move = cm[pos.piece_on(prevSq)][prevSq].second;
// Consider sligtly negative captures as good if at low depth and far from beta
if (ss && ss->staticEval < beta - PawnValueMg && d < 3 * ONE_PLY)
case KILLERS_S1:
cur = killers;
- end = cur + 3 - (killers[2].move == killers[0].move || killers[2].move == killers[1].move);
+ end = cur + 2;
+
+ if ((cur+3)->move && (cur+3)->move == (cur+2)->move) // Due to a SMP race
+ (cur+3)->move = MOVE_NONE;
+
+ // Be sure countermoves are different from killers
+ if ((cur+2)->move != cur->move && (cur+2)->move != (cur+1)->move)
+ end++;
+
+ if ((cur+3)->move != cur->move && (cur+3)->move != (cur+1)->move)
+ (end++)->move = (cur+3)->move;
return;
case QUIETS_1_S1:
if ( move != ttMove
&& move != killers[0].move
&& move != killers[1].move
- && move != killers[2].move)
+ && move != killers[2].move
+ && move != killers[3].move)
return move;
break;