|
Board-representation migration section 6: a GNUmakefile build flag
(-DGETATTACKS_BITBOARD) makes chess.h's GetAttacks macro resolve to
_GetAttacksBB instead of the real asm implementation (or SlowGetAttacks
under CROUTINES) -- a three-way choice at the same spot the existing
CROUTINES switch already lived. _GetAttacksBB is now reachable from
every real call site (generate.c's check-detection call, see.c's
SEE(), searchsup.c), not just the test/bench harness.
Found and fixed while verifying this: testsee.c's TestGetAttacks and
its benchmark call the identifier GetAttacks meaning "the real
asm/CROUTINES baseline" -- once the macro could resolve to
_GetAttacksBB, those calls would silently compare the new
implementation against itself, turning both the correctness sweep and
the benchmark into false-positive no-ops. Fixed with a local #undef
GetAttacks right after #include "chess.h" in testsee.c, so the harness
always validates against the true baseline regardless of which
implementation is live in production.
Verified: gmake TEST=1 GETATTACKS_BITBOARD=1 passes (self-test suite,
corrected benchmark still reporting real asm vs. _GetAttacksBB
correctly, and a real Search() call exercising _GetAttacksBB live).
precommit_check.sh GETATTACKS_BITBOARD=1 clean for both the TEST=1
self-test and DEBUG=1 smoke test. Default (no flag) build confirmed
unaffected -- GetAttacks still resolves to the real asm function.
See board_representation/MIGRATION.md section 6 for the full writeup.
Sections 4/5/7's remaining items (curated-suite sd10 comparison,
match_play.py gate) are now unblocked but not yet run.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Jntky4yGUTyQVaGCXms4F2
|
|
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 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Jntky4yGUTyQVaGCXms4F2
|
