Qwen2.5-1.5B-Instruct — DeepMath RAFT (Direct-OPD exp3, Part B)

pi_post^RAFT for the Direct-OPD mechanism experiment (pre-registration section F1–F4). Rejection-sampling SFT: Qwen/Qwen2.5-1.5B-Instruct @ 989aa7980e4cf806f80c7fef2b1adb7bc71aa306 fine-tuned on its own verified completions — k=4 samples at T 0.7 / top_p 0.95 per prompt over the pilot's sft_train split, math-verify-checked against DeepMath-103K ground truth, at most one correct sample kept per prompt.

The point of the pair (pi_pre, this model) is that it is SFT in mechanics but pi_post ~ pi_pre * exp(advantage) in distribution, so the Direct-OPD shift reward log pi_post - log pi_pre should behave like the RL pairs, not like the corpus-SFT pairs.

base Qwen/Qwen2.5-1.5B-Instruct @ 989aa7980e4cf806f80c7fef2b1adb7bc71aa306
data cmpatino/direct-opd-exp3-raft-data @ 5cd1dea4b139b22f2db98b56a734db34cb469743 :: raft_sft.parquet (4187 kept samples)
loss assistant-masked causal LM, token-weighted
epochs / steps 2 / 124
batch global 64 (2 x 32)
lr / schedule 1e-05, cosine decay, 6 warmup
precision fp32 master weights, bf16 autocast, bf16 checkpoints
val loss step 0 0.1688 -> final 0.1617
checkpoints checkpoint-25pct, checkpoint-50pct, checkpoint-75pct, checkpoint-100pct (+ final at root)

Checkpoint config.json, generation_config.json, tokenizer.json and tokenizer_config.json are byte-identical to the base snapshot; lm_head.weight is omitted because the embeddings are tied, exactly as in the base checkpoint.

Private research artefact for the Direct-OPD SFT-transfer study. Not a general-purpose model.

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