Nemotron-3 120B-A12B — Warm-Start SFT 200k (instruct)

This is one of four canonical warm-start baselines for the Geodesic Research SFM / inoculation campaigns. Models trained with this checkpoint as the starting point should be directly comparable across the {30B, 120B} × {think, instruct} matrix.

Variant

instruct — uses the geodesic-research/nemotron-instruct-tokenizer, whose chat template never auto-injects <think>...</think> reasoning tags. Inference produces direct instruct-style responses without reasoning traces..

The encoder is byte-identical to the upstream nvidia/NVIDIA-Nemotron-3-Super-120B-A12B-BF16 tokenizer; only the chat template differs from upstream.

Training data

  • HF dataset: geodesic-research/sft-warm-start-200k
  • Subset: no_think
  • Examples: 200,000 chat-format conversations (no held-out validation/test split)
  • Tokens: 259M (counted with the instruct tokenizer)
  • Sequence packing: pad_seq_to_mult=1, pad_to_max_length=false, packed sequence length 8192

Training recipe

Hardware Isambard GH200, 16 nodes × 4 GPUs (sm_90, BF16)
Parallelism TP=4, EP=4, PP=8, CP=1, ETP=1 (parallel folding)
Data parallelism DP_pure=2, grad_accum=32
Global batch size 64 (× 8192 tokens = 524k tokens/batch)
Sequence length 8192
Optimizer distributed Adam (β1=0.9, β2=0.95, ε=1e-8, wd=0.1, clip=1)
Learning rate 5e-06 (cosine decay to 0, 5% warmup)
Precision BF16 + Precision-Aware Optimizer (BF16 momentum/variance) + activation offloading
Iterations 495 (≈ 1 epoch over the dataset)
W&B run link
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