diff --git a/src/evaluate.cpp b/src/evaluate.cpp index 9756add8..cf684638 100644 --- a/src/evaluate.cpp +++ b/src/evaluate.cpp @@ -1146,7 +1146,11 @@ Value do_evaluate(const Position& pos, Value& margin) { behind |= (Us == WHITE ? behind >> 8 : behind << 8); behind |= (Us == WHITE ? behind >> 16 : behind << 16); - return popcount(safe) + popcount(behind & safe); + // Since SpaceMask[Us] is fully on our half of the board + assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0); + + // Count safe + (behind & safe) with a single popcount + return popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe)); }