| --- |
| license: other |
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| # BluScriptCP aligned mixes (2026-10-15) |
|
|
| Training mixes for long-context extension of the 1.70B fullchess model (GPT-2 tokenizer), |
| built by a new two-stage mixer: |
|
|
| 1. `mkmix_bucket.py` selects whole documents to hit TARGET domain shares and a TARGET |
| document-length profile at the same time (iterative proportional fitting under per-cell |
| supply caps; documents drawn uniformly at random within each domain x length cell). |
| 2. `mkpack_aligned.py` lays those documents out so that no document of length <= T is cut by |
| a training-window edge. Documents longer than T start a window and are chunked at |
| multiples of T from their own start; all others are placed whole, best-fit decreasing. |
| No padding: every window is exactly T tokens. |
|
|
| ## Contents |
|
|
| | folder | T | train tokens | windows (= T-token batches) | steps at 128 windows/step | what | |
| |---|---|---|---|---|---| |
| | `p1b_16k_aligned/` | 16,384 | 1,000,439,809 | 61,062 | 477 | **ready to train**: 4k->16k extension mix, aligned packing (`--float-tails`) | |
| | `p1b_16k_unaligned/` | 16,384 | 1,000,589,883 | -- | 477 | the same documents, plain concatenation (for comparison) | |
| | `p2d_32k_aligned/` | 32,768 | 600,473,601 | 18,325 | 143 | **ready to train**: 16k->32k extension mix, aligned packing | |
| | `p2c_32k_unaligned/` | 32,768 | 600,732,695 | -- | 143 | the same documents, plain concatenation (for comparison) | |
| | `tools/` | | | | | the mixer scripts and the statistics scripts | |
|
|
| Each mix folder holds `train_000000.bin`, `val_000000.bin` (raw uint16 GPT-2 tokens; EOT 50256 |
| marks the START of every document), `mix_report.json` (provenance and statistics) and |
| `selected.npz` where present (keys of the source documents used, to exclude them from later |
| mixes). `MANIFEST.txt` lists sha256 and byte size of every file. |
|
|
| ## Domain shares and length profile |
|
|
| | mix | code | math | commoncrawl | chess (Lichess) | stockfish | |
| |---|---|---|---|---|---| |
| | P1b | 37.0% | 29.0% | 28.0% | 3.0% | 3.0% | |
| | P2c / P2d | 40.0% | 29.1% | 24.9% | 3.0% | 3.0% | |
|
|
| Share of training tokens by whole-document length: |
|
|
| | mix | <4k | 4-16k | 16-32k | 32-64k | 64-128k | >=128k | |
| |---|---|---|---|---|---|---| |
| | P1b | 18.2 | 0.0 | 56.1 | 16.6 | 4.5 | 4.6 | |
| | P2c / P2d | 15.6 | 3.6 | 17.0 | 22.4 | 8.5 | 32.9 | |
|
|
| P1b copies the length profile of the 2026-10-05 ladder's P1 mix (including its empty 4-16k |
| bucket) with the 2026-10-13 ladder's domain shares. P2c/P2d copy the 2026-10-05 P2 profile |
| for the text part, with 6% chess added in <4k. |
|
|
| ## What aligned packing buys |
|
|
| Share of tokens with at least d tokens of same-document context inside their window: |
|
|
| | mix | packing | >= T/4 | >= T/2 | >= 3T/4 | |
| |---|---|---|---|---| |
| | P1b (T=16k) | plain | 52.1% | 28.5% | 11.2% | |
| | P1b (T=16k) | **aligned** | 56.4% | 35.4% | 16.9% | |
| | P2c/P2d (T=32k) | plain | 51.6% | 28.1% | 11.7% | |
| | P2c/P2d (T=32k) | **aligned** | 56.6% | 33.4% | 14.8% | |
|
|
| Packing cost: P2d drops 259,095 tokens (0.043%), P1b 180,274 (0.018%), all from short |
| "reserve" documents (<= 227 tokens) cut to close the last gaps. P1b additionally inserts one |
| EOT before each of 30,199 floated document tails (`--float-tails`: the last partial chunk of a |
| split document cannot see its own beginning in any layout, so it is placed like a short |
| document; strict alignment left 14.3% of window space empty for this length profile). |
|
|
| ## Using the aligned mixes |
|
|
| The layout assumes the loader reads window k as `train[k*T : (k+1)*T]` (+1 token for the |
| shifted target), starting at offset 0, sequentially - which is what BluScriptCP's |
| `DataLoaderLite` does with one data-parallel rank. A loader that reads at random offsets, or |
| with a different T, loses the alignment (the data is still valid, just no longer aligned). |
| Windows are shuffled at build time. The last token of each window predicts the first token of |
| an unrelated window (0.003% of targets). |
|
|
| Intended for training with intra-document masking (`CP_DOC_MASK=1`, EOT 50256): a window that |
| begins with a continuation chunk has no leading EOT and forms its own document id 0. |
|
|
| ## Source data |
|
|
| Selected from the fullchess pretraining shards (commoncrawl, code, math: navingv corpora; |
| Lichess `chess_v2` 1-epoch; Stockfish `adamkarvonen/chess_games` stockfish_dataset). These |
| documents were already seen once during fullchess pretraining. |
| |
