typhoon.git/src/board_representation/EVAL.md, branch master

Update EVAL.md: progress log, lessons learned, corrected next steps

2026-09-05T09:22:58Z

Records what's actually landed (pawns, bbOccupied, dispatch loop, knight, bishop -- commits 57502d6/2ce3570/6e86450/7e3e6b6/de3f366), corrects section 4's per-piece #define toggle strategy (not what was actually used -- direct incremental rewrites with transitional helpers instead), and documents methodology worth repeating: - One piece type at a time, each landed and verified before the next starts, learned the hard way after a combined knight+bishop+rook+ queen+king attempt produced a real bug that was hard to isolate with five things changed at once and had to be reverted. - Keep writing DEBUG asserts against the still-live rgSquare mailbox representation as independent ground truth for as long as it exists -- this is specifically what caught bishop's x-ray-chain behavior gap during routine smoke testing. - Verification bar changes once a step ships a deliberate behavior change (bishop's x-ray simplification): full ecm_ringers solve parity + bounded node-count deltas, not byte-identical counts. - This effort errs on the side of speed over exact fidelity, explicitly -- a real, recorded change from the original plan's "must be byte-identical" bar. - What's next: rook, then queen, then _EvalKing/_WhoControlsSquareFast, culminating in deleting bvAttacks/ATTACK_BITV/the c|8 mechanism entirely once nothing writes it anymore. Transitional helpers get rewritten incrementally as each piece converts, not left to accumulate special cases. - Pawn hash hit/miss cost measurements (90 vs 1741 cycles) and the EVAL_TIME per-term breakdown methodology, both worth reusing on rook/queen once they land. - Noted intent to revisit the non-mobility scoring terms in _EvalKnight/_EvalBishop/_EvalRook/_EvalQueen once the attack-bits work is done -- separate, later pass, not scoped further yet. Co-Authored-By: Claude Sonnet 5 Claude-Session: https://claude.ai/code/session_01P6g6iF6mD1Hau6nCZCzwYj

Maintain pos->bbOccupied incrementally, dedupe its two from-scratch builders

2026-09-05T07:19:59Z

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

Add Eval() bitboard-migration plan, per-term EVAL_TIME cycle breakdown, drop redundant pawn-location bitboard

2026-09-05T06:54:51Z

board_representation/EVAL.md: rewritten migration plan for a bitboard-backed Eval() (mobility ray-walks + bvAttacks replacement), plus a performance-philosophy section recording the profiling-first, cut-aggressively-except-mobility/safety-awareness approach agreed on this session, and findings on CountKingSafetyDefects' structural inability to share bvAttacks-derived state with _EvalKing. EVAL_TIME per-term instrumentation (chess.h/eval.c/root.c): breaks the existing whole-Eval() cycle counter down by pawns/knight/bishop/ rook/queen/king, the always-paid pre-lazy-exit segment, and the full-eval-only post-lazy segment, printed alongside the existing "Avg. cpu cycles in eval" line. Diagnostic only (EVAL_TIME-gated), no effect on the normal release profile. Drop PAWN_HASH_ENTRY's bbPawnLocations[2]: it duplicated POSITION's own incrementally-maintained bbPawns[2], rebuilt bit-by-bit on every pawn-hash miss for no reason. eval.c now reads pos->bbPawns[] directly; removed a stale per-iteration invariant assert in _EvalPawns that only made sense when the bitboard was being built bit-by-bit in that same loop. Co-Authored-By: Claude Sonnet 5 Claude-Session: https://claude.ai/code/session_01P6g6iF6mD1Hau6nCZCzwYj