From 5c8d794782d3be6368dbba613ef129b11d878d97 Mon Sep 17 00:00:00 2001 From: Scott Gasch Date: Fri, 4 Sep 2026 01:03:00 -0700 Subject: Fix passed-pawn bitboard bit-clear bug, LMR gate coupling, inline hot bitboard helpers - bitboard.c: CoorFromBitBoardRank1ToRank8 cleared the lowest set bit unconditionally instead of the reported (highest) one, silently mis-walking doubled-pawn files in eval.c's passed-pawn detection. - search.c/searchsup.c: move GetLMRReduction's precondition checks from inside the function to the caller in search.c (pre-existing work), finishing the split with a matching gate in split.c's HelpSearch -- the parallel-search call site had no gate at all, letting it call GetLMRReduction unconditionally (including for checking moves), reachable only under real multithreading (--cpus > 1) and the intermittent root cause of assertion crashes seen under --cpus 4. - eval.c: redirect CountBits/CoorFromBitBoardRank8ToRank1/ CoorFromBitBoardRank1ToRank8 to inline compiler-builtin versions (gated !CROUTINES) instead of the real out-of-line asm calls, on eval.c's ~20 existing production call sites. CountBits' asm body isn't O(1) popcnt, it's a Kernighan bit-clearing loop plus call overhead, paid on every Eval() call. Co-Authored-By: Claude Sonnet 5 Claude-Session: https://claude.ai/code/session_01Jntky4yGUTyQVaGCXms4F2 --- src/search.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'src/search.c') diff --git a/src/search.c b/src/search.c index 807f69d..1b83891 100755 --- a/src/search.c +++ b/src/search.c @@ -664,7 +664,7 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx, // underflow (ULONG) in that case, which is exactly why the // uDepth >= ONE_PLY check below short-circuits before the // g_fCanSplit[] indexing ever evaluates it. - if (((uLegalMoves >= 3)) && + if (((uLegalMoves >= 2) && fIsLeftoverMove) && (0 != g_uNumHelpersAvailable) && (FALSE == pi->fMovesRescoredByIID) && (0 == uFutilityMargin) && @@ -750,6 +750,14 @@ Search(IN SEARCHER_THREAD_CONTEXT *ctx, // Decide how much (if any) to reduce this move's depth -- // graded LMR. + if ((uDepth > TWO_PLY) && + !pi->fPvNode && + !(ctx->sPlyInfo[ctx->uPly - 1].fPvNode) && + (uLegalMoves > 5) && + (0 == iExtend) && + (!IS_ESCAPING_CHECK(mv)) && + (!IS_CAPTURE_OR_PROMOTION(mv)) && + (!IS_CHECKING_MOVE(mv))) { INT iLMR = GetLMRReduction(iEval, iAlpha, -- cgit v1.3