peterwooden/chess-gpt-demo-ngram

Chess GPT demo SAN n-gram

This is the first playable teaching baseline from peterwooden/chess-gpt. It is a count-based backoff n-gram model, not a neural network or Transformer, and exists to establish a reproducible floor before neural experiments begin. It predates the agreed 2026 tournament corpus and is not tournament-eligible.

Play it

Open the Chess GPT browser arena and load this pinned package reference:

peterwooden/chess-gpt-demo-ngram@bea221167728c33f0a5df54051cd27717cae6586

The browser verifies every declared file before running the adapter locally in a dedicated Worker.

Interface

• Input: the complete game history as standard algebraic notation (SAN) moves.
• Output: exactly one legal SAN move.
• Policy: use the most frequent legal continuation of the last two moves; back off to a one-move context, then side-to-move frequencies, then a deterministic legal fallback.
• Package: chess-gpt-package-v1 with a self-contained browser/entry.js, canonical browser/model.json, and hashed browser/manifest.json.

Training and evaluation

• Dataset: shazmate/lichess-chess-tokens
• Dataset revision: cb90f1bb2eab0b905e84e14f2d1d24ec5f9d1d94
• Games processed: 10,000
• Split: deterministic whole-game split; 8,990 training games and 1,010 validation games
• Validation top-1 accuracy: 22.41%
• Validation legal-move rate: 100%
• Compressed checkpoint: 1,412,649 bytes
• Canonical learned state: 6,687,169 bytes
• Checkpoint SHA-256: c143646b163c8c91c39bc654bf9a57d0a142bf010ec7b9c90971248616103f1c
• Canonical package: 6,689,698 bytes
• Manifest SHA-256: fc1160f487f315036fc320a7e7ced5a2e8cf9872345318a2959f8f727b949702

The full machine-readable record is in metrics.json. The experiment specification and implementation live in the source repository as experiment 0001-basic-san-ngram.

Limitations

This model recognizes short statistical continuations; it does not evaluate positions, search variations, or understand long-range plans. Validation next-move accuracy is not a claim about playing strength. Expect weak and sometimes strange chess—the point is to make the first floor observable and beatable.