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Condense the tokenizer section of the model card

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  1. README.md +6 -29
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@@ -38,35 +38,12 @@ The bundled tokenizer is configured the way the training corpus was encoded:
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  repository's own defaults differ on both points, so encode through the
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  tokenizer shipped here rather than re-fetching it by name.
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- **To condition on the start of a document, prefix the EOS token, not a BOS.**
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- Training packed documents as `[text..., EOS]`, so the token preceding any
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- document's first token is always the EOS; a BOS was never seen at any position.
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- Measured on held-out documents at 1.3B, against a bare prompt:
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-
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- | prefix | mean NLL | first 8 tokens |
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- |---|---|---|
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- | none | 2.0104 | 3.2947 |
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- | **EOS** | **1.9960** | **2.9606** |
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- | BOS | 2.0150 | 3.3768 |
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-
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- So the EOS is worth ~0.33 nats on the opening tokens and the BOS costs ~0.08.
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-
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- **Only at a document start.** The prefix is a "a new document begins here"
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- signal, and mid-document it is a false one — on continuations the same EOS
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- prefix *costs* 0.34 nats over the first 8 tokens (2.19 → 2.22 overall). Prefix
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- it when you mean a fresh document; leave a continuation bare. Nothing in the
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- weights or the tokenizer can tell these apart, which is why this is the
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- caller's decision.
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-
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- `bos_token` is remapped to `</s>` here, so a pipeline that asks for "the BOS"
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- (lm-eval's `--add_bos_token`, a generic wrapper) gets the separator rather than
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- the unused `<s>`. `add_bos_token` remains `False`, so the default is still a
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- bare prompt — which is the convention every number quoted for these models was
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- measured under.
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-
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- If you are coming from `fla-hub` checkpoints, note that they use the opposite
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- convention -- trained as `[BOS, text...]` with the BOS as the document
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- separator -- so the habit does not carry over.
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  ## Usage
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  repository's own defaults differ on both points, so encode through the
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  tokenizer shipped here rather than re-fetching it by name.
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+ **To condition on the start of a document, prefix the EOS token** -- that is
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+ what precedes every document's first token in training, and a BOS was never
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+ seen at any position. Leave a continuation bare: mid-document the prefix is a
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+ false signal and costs accuracy. `bos_token` is remapped to `</s>` here, so a
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+ caller that asks for "the BOS" gets the separator, while `add_bos_token` stays
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+ `False` and the default remains a bare prompt.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  ## Usage
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