Progress report — 2026-07-10 / 2026-07-11
Session goal: push the latest 200M compact-vocab ChessTransformer toward high Elo without MCTS (pure next-move / policy argmax), while growing better soft-target data.
Summary
| Item | Result |
|---|---|
| Base model | avewright/chess-transformer-200m-compact-soft |
| Finetune run | exp189 — soft MultiPV + hard deep labels + h-flip |
| Deep data harvest | exp190 — phase-balanced SF18 MultiPV (ongoing) |
| Checkpoint pushed | latest step 2851, best by holdout metric at step 500 |
| Pure-policy Elo (vs SF18 limited) | ~1700 (bracket 1500–1800) |
| Training status | Stopped on request after plateau |
What we shipped (code)
| Path | Role |
|---|---|
experiments/exp189_200m_maxelo_policy.py |
Max-Elo policy finetune; mixes shallow soft + deep soft + hard HF |
experiments/exp190_phase_deep_harvest.py |
Phase-quota MultiPV harvest (SF18, Syzygy, multi-source FENs) |
scripts/run_exp189_200m_maxelo.sh |
Initial exp189 launch |
scripts/run_exp189_deep_mix.sh |
Resume with --deep-soft-cache mix |
scripts/run_exp190_phase_deep.sh |
Harvest launcher (40 workers, SF18 vnni512) |
play_factory_gui.py |
Fix: Chess960 castling UCI (e8a8) → standard (e8c8) for chess.js |
Training recipe (exp189)
Resumed from compact-soft, then continued with deep-mix:
- Soft frac 0.72, soft α 0.40, deep-mix frac 0.40 among soft steps
- Batch 448 × 2 accum, LR 4e-6 cosine, warmup 200
- H-flip aug p=0.5 on soft batches
- Hard ballast: HF lichess-sf stream,
min_depth≥15 - Eval: shallow holdout + deep holdout;
best.pttracks blended top-1
Observed learning
Deep-mix run plateaued around:
- Shallow soft holdout top-1 ≈ 38%
- Deep soft holdout top-1 ≈ 41%
- Blended best metric 0.3966 recorded at step 500 of the deep-mix resume
- Shutdown save:
latest.ptat step 2851
Losses stayed flat (soft 2.38, hard CE ~1.79) — model had largely extracted the
signal from the then-available mix (2M shallow + ~96–175k deep).
Soft targets — why they matter
Hard labels = one Stockfish best move. Soft MultiPV labels = a distribution over plausible moves (score → softmax). That teaches:
- Near-equal alternatives (not overconfident on one line)
- Better calibration under legal-mask argmax (no search)
- Deeper MultiPV (exp190) = sharper teacher in middlegame/endgame
exp186 already provided ~2M shallow soft rows (avewright/exp186-sf-multipv-2m).
exp190 adds phase-balanced deeper labels so training does not drown in openings.
exp190 harvest design
Targets: 22% opening / 48% middlegame / 30% endgame
| Lever | Design |
|---|---|
| Depth-by-phase | opening 10–14, mid 12–16, endgame 14–18 |
| Teacher | Stockfish 18 full strength (stockfish/stockfish-latest vnni512) |
| Sources | HF streams + book playouts + endgame templates + random walks |
| Quotas | Deficit-first producer + hard gate at writer |
| Tags | phase, label_depth in soft_cache.pt for stratified training |
| Syzygy | Workers probe tablebases when present |
At upload time harvest was ~187k written positions (target 1M, still running),
phase mix roughly on quota. See outputs/exp190_phase_deep/ARCHITECTURE.md.
Elo evaluation
Script: elo_eval_latest.py
Checkpoint: outputs/exp189_200m_maxelo_policy/latest.pt
Opponent: SF18 UCI_LimitStrength, 50ms/move, 8 openings × both colors, Syzygy + book.
| SF Elo | Score | W–D–L |
|---|---|---|
| 1500 | 0.625 | 7–6–3 |
| 1800 | 0.438 | 4–6–6 |
Estimated Elo ≈ 1700 (noisy; ±~150 with this sample).
Weakness: Black side (more losses / short mates). No MCTS at inference.
Hugging Face artifacts
| Repo | Type | Contents |
|---|---|---|
avewright/chess-transformer-200m-maxelo |
model | best_model.pt, latest_model.pt, config, Elo + progress docs |
avewright/exp190-phase-deep-soft |
dataset | soft_cache.pt, jsonl shards, status, architecture notes |
Base still: avewright/chess-transformer-200m-compact-soft
Shallow soft still: avewright/exp186-sf-multipv-2m
How to load for inference
export MOVE_VOCAB_VERSION=compact
python play_factory_gui.py --checkpoint path/to/latest_model.pt
# or
python elo_eval_latest.py path/to/latest_model.pt
Policy-only: legal-mask argmax on policy_logits (see elo_eval_latest.get_model_move_generic).
Next levers (not done this session)
- Grow exp190 to 1M+ and retrain with stratified phase sampling + depth weights
- Longer Elo gauntlet (more games / level) and evaluate
bestvslatest - AlphaZero-style expert iteration (
exp183_selfplay.py/rl_selfplay/) after supervised plateau - Fix Black-side weakness (phase-balanced Black STM oversampling, or STM-normalized training audit)
Ops notes
- Training stopped cleanly:
Saved on shutdown at step 2851 - Harvest left running on CPU (40 workers) so it does not starve a future GPU train
.env/ tokens are gitignored — never commit HF or GitHub secrets