File size: 2,756 Bytes
0040de1 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 | """Extract every FEN from a Stockfish .plain file.
This replaces filter_plain.py for consumers that want positions rather than
Stockfish NNUE training samples. filter_plain.py drops any position holding
castling rights that did not arise from a standard opening, because Stockfish
cannot train on Chess960 castling. Nothing here is dropped by default: the
positions are the product, and which ones to keep is the caller's decision.
Chess960 positions are recognised and counted, and can be excluded with
--standard-only. They are reported either way, so the composition of the output
is never silent.
"""
from __future__ import annotations
import argparse
import gzip
import sys
from pathlib import Path
# Shredder-FEN castling fields name the rook files, so anything outside KQkq is
# a Chess960 game. lc0's test80 run mixes a small share of them into self-play.
STANDARD_CASTLING = set("KQkq-")
def is_chess960(fen: str) -> bool:
field = fen.split(" ")[2]
return not set(field) <= STANDARD_CASTLING
def opened(path: Path, mode: str):
if path.suffix == ".gz":
return gzip.open(path, mode + "t", encoding="utf-8")
return open(path, mode, encoding="utf-8")
def convert(source: Path, destination: Path, standard_only: bool) -> dict[str, int]:
counts = {"positions": 0, "chess960": 0, "written": 0}
with opened(source, "r") as infile, opened(destination, "w") as outfile:
for row in infile:
if not row.startswith("fen "):
continue
fen = row[4:].strip()
counts["positions"] += 1
frc = is_chess960(fen)
counts["chess960"] += frc
if standard_only and frc:
continue
counts["written"] += 1
outfile.write(fen + "\n")
return counts
def main() -> None:
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument("input", type=Path, help="a .plain or .plain.gz file")
parser.add_argument("-o", "--output", type=Path)
parser.add_argument(
"--standard-only",
action="store_true",
help="drop Chess960 positions instead of keeping them",
)
args = parser.parse_args()
destination = args.output
if destination is None:
stem = args.input.name.replace(".plain.gz", "").replace(".plain", "")
destination = args.input.with_name(stem + ".fen")
counts = convert(args.input, destination, args.standard_only)
print(
f"{args.input} -> {destination}\n"
f" positions read: {counts['positions']:,}\n"
f" chess960: {counts['chess960']:,}\n"
f" written: {counts['written']:,}",
file=sys.stderr,
)
if __name__ == "__main__":
main()
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