From 2ce3570dc6aa67f82dd6f02fc4e518be3e33aabf Mon Sep 17 00:00:00 2001 From: Scott Gasch Date: Sat, 5 Sep 2026 00:19:59 -0700 Subject: Maintain pos->bbOccupied incrementally, dedupe its two from-scratch builders chess.h: add POSITION::bbOccupied (full-board occupancy, both colors, every piece including kings), maintained incrementally alongside bbPieces/bbPawns rather than rebuilt on demand -- resolves the open question in EVAL.md section 0 about whether this is worth doing given both generate.c and the planned eval.c mobility rewrite need it. move.c: SlidePiece/SlidePawn/LiftPiece/PlacePiece and their WithoutSigs variants now maintain bbOccupied at the same choke points that already maintain bbPieces/bbPawns -- unconditionally, since occupancy doesn't care about piece type or color. Kings only ever move through SlidePiece/SlidePieceWithoutSigs (never Lift/Place), so no separate king-specific update site was needed. fen.c: populate bbOccupied when parsing a FEN. board.c: VerifyPositionConsistency cross-checks pos->bbOccupied against a from-scratch rebuild, same pattern already used for bbPieces/bbPawns. generate.c/movesup.c/see.c: replace call sites that rebuilt full occupancy via _BuildFullOccupiedBB/_BuildOccupiedBB with direct reads of pos->bbOccupied; delete see.c's _BuildOccupiedBB, which was a byte-for-byte duplicate of generate.c's _BuildFullOccupiedBB (kept only as the from-scratch ground truth for the new consistency check and testgenerate.c's benchmark harness). testsup.c: GenerateRandomLegalPosition builds POSITIONs by poking rgSquare/bbPieces/bbPawns directly, bypassing both move.c and fen.c -- a third construction path the above missed. It never set bbOccupied, so the new VerifyPositionConsistency check failed on every generated position, and since generation retries until a position verifies, the self-test suite spun forever (100% CPU, no progress) instead of crashing outright. Fixed by setting bbOccupied at all four placement sites (both kings, pawn, non-pawn piece). Full self-test suite and precommit_check.sh verified clean afterward. board_representation/EVAL.md: record the bbOccupied decision and rationale, resolving section 0's open question. Co-Authored-By: Claude Sonnet 5 Claude-Session: https://claude.ai/code/session_01P6g6iF6mD1Hau6nCZCzwYj --- src/movesup.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'src/movesup.c') diff --git a/src/movesup.c b/src/movesup.c index 22bf0c1..82ba10a 100755 --- a/src/movesup.c +++ b/src/movesup.c @@ -220,7 +220,7 @@ Return value: iDelta = CHECK_DELTA_WITH_INDEX(iIndex); ASSERT(iDelta != 0); - bbOccupiedWithoutRemove = _BuildFullOccupiedBB(pos) & ~COOR_TO_BB(cRemove); + bbOccupiedWithoutRemove = pos->bbOccupied & ~COOR_TO_BB(cRemove); cBlocker = _NearestBlockerAlongRayBB(cLocation, iDelta, bbOccupiedWithoutRemove); return _ValidateExposedBlockerBB(pos, cBlocker, cLocation); @@ -270,7 +270,7 @@ Return value: } iDelta = CHECK_DELTA_WITH_INDEX(iIndex); - bbOccupiedWithoutRemove = _BuildFullOccupiedBB(pos) & ~COOR_TO_BB(cRemove); + bbOccupiedWithoutRemove = pos->bbOccupied & ~COOR_TO_BB(cRemove); cBlocker = _NearestBlockerAlongRayBB(cLocation, iDelta, bbOccupiedWithoutRemove); return _ValidateExposedBlockerBB(pos, cBlocker, cLocation); @@ -323,7 +323,7 @@ Return value: } iDelta = CHECK_DELTA_WITH_INDEX(iIndex); - bbOccupied = (_BuildFullOccupiedBB(pos) & + bbOccupied = (pos->bbOccupied & ~COOR_TO_BB(cTest) & ~COOR_TO_BB(cIgnore)) | COOR_TO_BB(cBlock); cBlocker = _NearestBlockerAlongRayBB(cKing, iDelta, bbOccupied); @@ -641,7 +641,7 @@ Return value: ASSERT(IS_ON_BOARD(cTest)); ASSERT(IS_VALID_COLOR(uSide)); - bbOccupied = _BuildFullOccupiedBB(pos); + bbOccupied = pos->bbOccupied; if (0 != _WhoAttacksSquareBB(pos, cTest, uSide, bbOccupied)) { return(TRUE); -- cgit v1.3