From be420bb8d1d5d16a4e24ab6fd706a5ae898eaa85 Mon Sep 17 00:00:00 2001 From: Scott Gasch Date: Fri, 4 Sep 2026 09:22:46 -0700 Subject: Add bitboard-backed GetAttacks (section 2/3), verified faster than asm Board-representation migration, sections 2-3 (GetAttacks half): - board.c: VerifyPositionConsistency's bbPieces consistency check (migration section 2), verified clean via gmake TEST=1 with the assert live. - POSITION.bbPawns[2]: new incrementally-maintained per-color pawn location bitboard (chess.h), maintained at the same 6 move.c sites as bbPieces, populated from scratch in fen.c. Distinct from the pawn-hash-keyed bbPawnLocations; this one needs no SEARCHER_THREAD_CONTEXT, so it's reachable from GetAttacks's actual call sites (which only ever have a POSITION*). - data.c/chess.h/main.c: g_RookRayAll/g_BishopRayAll (all 4 per-square ray directions pre-ORed) and g_PawnAttackOriginBB[2][128] startup tables, plus FastFirstBit/FastLastBit (static inline bsf/bsr wrappers, chess.h) -- supporting tables/helpers for the primitive below. - see.c: _WhoAttacksSquareBB (bitboard "who attacks square X" query) and _GetAttacksBB (SEE_LIST-populating PoC wrapping it), side by side with the existing SlowGetAttacks/asm GetAttacks -- not wired into the GetAttacks macro yet (section 6), pure addition. - testsee.c: SeeListsAreEqual made order-independent (SEE() sorts the list right after GetAttacks returns, so order was never semantically significant); TestGetAttacks extended to run _GetAttacksBB as a third comparison across the existing 20,000-random-position sweep; added an interleaved asm/Slow/BB cycles-per-call benchmark across opening/middlegame/endgame positions. - testsup.c: fixed GenerateRandomLegalPosition (used by the sweep above) to maintain bbPieces/bbPawns at its two hand-placement sites -- a latent gap since section 1 that made its own VerifyPositionConsistency legality gate almost always reject generated positions, causing large, variable retry-loop slowdowns. Verified: 20,000-position x every-square x both-colors correctness sweep passes (gmake TEST=1), precommit_check.sh clean (self-test + DEBUG smoke test). Benchmark: _GetAttacksBB is ~0.53-0.55x asm GetAttacks's cycles/call (opening/middlegame) and ~0.89x (endgame) -- faster, not just equivalent, primarily from replacing bbOccupied's up-to-16-iteration pawn loop with two bbPawns ORs, plus a g_PawnAttackOriginBB table lookup replacing per-call pawn-delta arithmetic and per-direction/per-side-group early-outs in the slider walk. See board_representation/MIGRATION.md section 3 for the full writeup, including a reverted approach that measured slower and why, and the CountKingSafetyDefects half's re-scoped (not yet implemented) design. Also confirmed (not caused by this work, not fixed here): a pre-existing non-deterministic MP-race assertion in util.c:1093's PV printing, reproduced independently on a clean HEAD checkout. Co-Authored-By: Claude Sonnet 5 Claude-Session: https://claude.ai/code/session_01Jntky4yGUTyQVaGCXms4F2 --- src/board.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'src/board.c') diff --git a/src/board.c b/src/board.c index 0c5f4df..0b195be 100755 --- a/src/board.c +++ b/src/board.c @@ -169,6 +169,7 @@ Return value: "Extra pieces on board that are not accounted for", "Fifty move counter is too high", "bbPieces bitboard doesn't match piece list", + "bbPawns bitboard doesn't match pawn list", }; ULONG u, v; COOR c; @@ -177,6 +178,7 @@ Return value: ULONG uNonPawnMaterial[2] = {0, 0}; ULONG uNonPawnCount[2][7]; BITBOARD bbPieces[2][8]; + BITBOARD bbPawns[2]; ULONG uSigmaNonPawnCount[2] = {0, 0}; ULONG uWhiteSqBishopCount[2] = {0, 0}; UINT64 u64Computed; @@ -186,6 +188,7 @@ Return value: memset(uNonPawnCount, 0, sizeof(uNonPawnCount)); memset(bbPieces, 0, sizeof(bbPieces)); + memset(bbPawns, 0, sizeof(bbPawns)); u64Computed = ComputeSig(pos); if (pos->u64NonPawnSig != u64Computed) { @@ -268,6 +271,7 @@ Return value: } uPawnMaterial[u] += VALUE_PAWN; uPawnCount[u]++; + bbPawns[u] |= COOR_TO_BB(c); } } @@ -364,6 +368,12 @@ Return value: } } + if (pos->bbPawns[u] != bbPawns[u]) + { + uReason = 22; + goto end; + } + // // Note: the 0th spot in the array is the sum of all non pawns // -- cgit v1.3