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#!/usr/bin/env python3
"""Bit-for-bit cross-checker: diffs nnue_feature_spec.py's (Python)
HalfKAv2_hm feature indices against ../src/nnuefeatures.c's (C,
`dump nnuefeatures`) indices, for a set of hand-picked FENs chosen to
exercise every piece type, both king-file halves (a-d / e-h), both
perspectives, and non-symmetric positions (the starting position
alone can't catch a perspective-swap bug, since it's symmetric under
the exact transform between perspectives -- see NNUE.md).
Must pass before any training data is trusted to be feature-indexed
consistently between the Python trainer and the C inference code.
Usage:
python3 cross_check_features.py [--engine ../src/typhoon]
"""
import argparse
import re
import subprocess
import sys
from pathlib import Path
from nnue_feature_spec import active_feature_indices, chess
NNUE_RE = re.compile(r"^NNUE_FEATURES (white|black) (.*)$")
# (label, FEN) -- deliberately includes:
# - the symmetric starting position (sanity baseline only, see above)
# - both kings on the queenside half (a-d files) and kingside half (e-h)
# - a mixed case: White king queenside, Black king kingside (and the
# reverse), to catch a perspective/orientation mixup
# - every piece type present at least once, including promoted/extra
# queens and multiple same-type pieces
# - a near-empty king-and-pawns endgame (sparse feature set, edge of
# the active-feature-count range)
TEST_POSITIONS = [
("startpos",
"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"),
("both_kings_queenside",
"2kr4/8/8/8/8/8/8/2KR4 w - - 0 1"),
("both_kings_kingside",
"4rk2/8/8/8/8/8/8/4RK2 w - - 0 1"),
("white_queenside_black_kingside",
"4rk2/8/8/8/8/8/8/2KR4 w - - 0 1"),
("white_kingside_black_queenside",
"2kr4/8/8/8/8/8/8/4RK2 w - - 0 1"),
("midgame_mixed_material",
"r1bqk2r/pp1nbppp/2p1pn2/3p4/2PP4/2N1PN2/PP2BPPP/R1BQK2R w KQkq - 0 8"),
("sparse_king_pawn_endgame",
"8/5k2/8/3K4/8/8/5P2/8 w - - 0 1"),
("extra_queens",
"3qk3/3q4/8/8/8/8/3Q4/3QK3 w - - 0 1"),
("black_to_move_midgame",
"r2q1rk1/ppp2ppp/2n1bn2/2b1p3/4P3/2NPB3/PPP2PPP/R2Q1RK1 b - - 0 10"),
]
def run_engine_dump(engine, fen):
cmd = [
str(engine), "--cpus", "1", "--hash", "8m", "--logfile", "-",
"--batch", "--command",
f"force; setboard {fen}; dump nnuefeatures",
]
out = subprocess.run(cmd, capture_output=True, text=True, timeout=30).stdout
result = {}
for line in out.splitlines():
m = NNUE_RE.match(line.strip())
if m:
side, rest = m.groups()
result[side] = sorted(int(x) for x in rest.split()) if rest else []
return result
def main():
ap = argparse.ArgumentParser(description=__doc__)
ap.add_argument("--engine", default="../src/typhoon")
args = ap.parse_args()
engine = Path(args.engine).resolve()
if not engine.exists():
sys.exit(f"engine not found: {engine} (build it first -- see CLAUDE.md)")
n_ok = 0
n_fail = 0
for label, fen in TEST_POSITIONS:
board = chess.Board(fen)
py = {
"white": active_feature_indices(board, chess.WHITE),
"black": active_feature_indices(board, chess.BLACK),
}
c_out = run_engine_dump(engine, fen)
ok = True
for side in ("white", "black"):
if side not in c_out:
print(f"[{label}] FAIL: engine produced no '{side}' line at all")
ok = False
continue
if py[side] != c_out[side]:
ok = False
py_set, c_set = set(py[side]), set(c_out[side])
print(f"[{label}] FAIL ({side}): "
f"python={len(py[side])} idx, C={len(c_out[side])} idx")
only_py = sorted(py_set - c_set)
only_c = sorted(c_set - py_set)
if only_py:
print(f" only in python: {only_py}")
if only_c:
print(f" only in C: {only_c}")
if ok:
n_ok += 1
print(f"[{label}] OK ({len(py['white'])} features/perspective)")
else:
n_fail += 1
print(f" FEN: {fen}")
print(f"\n{n_ok} passed, {n_fail} failed, out of {len(TEST_POSITIONS)} positions")
sys.exit(1 if n_fail else 0)
if __name__ == "__main__":
main()
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