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- Create Date May 14, 2026
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LesChats-V.1.3-140526
IJCCRL Verified
LesChats V.1.3 is the new audited release of the IJCCRL opening book, delivered as a
Polyglot/BIN book file. This update replaces the previous public LesChats-110326
announcement with a quantified structural audit of the new binary book: file size, number of entries, number of
unique keyed positions, root move weights, line density, and a direct 16-ply traversal sample extracted from the book.
- Version update: from
LesChats-110326toLesChats V.1.3. - Delivered file:
LesChats-V.1.3.bin. - Book format: Polyglot/BIN, using 16-byte book records.
- File size: 146,959,472 bytes — approximately 146.959 MB / 140.151 MiB.
- Total book entries: 9,184,967.
- Unique keyed positions: 8,983,380.
- SHA-256:
a8088b9c2c98e33ad822c4e778552060d0a2c8a38bb8977d0b93f0986c356c34.
This is a measured release note, not a marketing statement. The figures above are extracted from the supplied
.bin book file and describe the structure of the book surface.
The previous public block described LesChats-110326 as a CTG/Fritz-compatible release. The new uploaded
release is a Polyglot/BIN book, so the publication text has been corrected to match the real delivered
asset.
- Previous public wording: CTG / Fritz GUI workflow.
- New published wording: Polyglot/BIN opening book workflow.
- Reason: the supplied release file is
LesChats-V.1.3.bin.
The previous HTML explained the update in general terms: broader coverage, more depth, and a stronger practical
opening surface. The new version adds measurable book data, making the release more transparent and easier to
audit.
- Total entries: 9,184,967 book moves.
- Unique positions: 8,983,380 keyed book positions.
- Average move density: 1.022 moves per keyed position.
- Maximum alternatives in one position: 15 book moves.
The new book is not a loose collection of many random alternatives per position. Its structure is strongly
consolidated: most keyed positions contain one selected continuation, with limited branching where the book
retains multiple practical choices.
- Positions with exactly one book move: 8,792,852 — 97.879% of unique positions.
- Positions with 2–4 book moves: 190,013 — 2.115% of unique positions.
- Positions with 5–8 book moves: 504 — 0.006% of unique positions.
- Positions with 9 or more book moves: 11 positions.
At the start position, the book exposes two root moves: 1.e4 and 1.d4. In this new
release, the root weights are no longer a visually neutral statement of equal practical preference. The weighted
root surface favours 1.e4.
- 1.e4: weight 65,520 — approximately 70.0% of the root weighted surface.
- 1.d4: weight 28,080 — approximately 30.0% of the root weighted surface.
- Interpretation: this is a book-weight observation, not an Elo or strength claim.
The following line is a deterministic high-weight traversal from the start position, extracted from the supplied
LesChats-V.1.3.bin book. It is included as a structural audit sample, not as a claim of engine superiority
or theoretical finality.
1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. d3 Bc5 5. c3 O-O 6. O-O d5 7. Nbd2 dxe4 8. dxe4 Qe7r1b2rk1/ppp1qppp/2n2n2/1Bb1p3/4P3/2P2N2/PP1N1PPP/R1BQ1RK1 w - - 1 9
A Stockfish 18 depth-8 evaluation pass should only be published after running the exact Stockfish 18 binary with
fixed UCI settings, fixed hash, fixed thread count, and a cleared hash before each FEN. No engine evaluation is
inferred from the book structure alone.
LesChats V.1.3 is a measurable structural update of the LesChats opening book. The new release is
published as a Polyglot/BIN book, contains 9.18 million book entries across
8.98 million unique keyed positions, and shows a highly consolidated continuation profile. Compared
with the previous public HTML, this update replaces broad descriptive language with direct file-level evidence:
format, size, entry count, unique-position count, root weights, line-density distribution, checksum, and a reproducible
16-ply traversal sample.