beta = std::min(mate_in(ss->ply+1), beta);
if (alpha >= beta)
return alpha;
+
+ // Check if there exists a move which draws by repetition, or an alternative
+ // earlier move to this position.
+ if ( pos.rule50_count() >= 3
+ && alpha < VALUE_DRAW
+ && pos.has_game_cycle(ss->ply))
+ {
+ alpha = VALUE_DRAW;
+ if (alpha >= beta)
+ return alpha;
+ }
}
assert(0 <= ss->ply && ss->ply < MAX_PLY);
&& (ss-1)->statScore < 22500
&& eval >= beta
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
- && !ss->excludedMove
+ && !excludedMove
&& pos.non_pawn_material(pos.side_to_move())
&& (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
{
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
}
// Bonus for prior countermove that caused the fail low
- else if ( depth >= 3 * ONE_PLY
+ else if ( (depth >= 3 * ONE_PLY || PvNode)
&& !pos.captured_piece()
&& is_ok((ss-1)->currentMove))
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));