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…vision (#1905) fix(gemma4_moe): use vision-aware attention mask when use_bidirectional_attention="vision" Gemma4 multimodal variants with `use_bidirectional_attention="vision"` in their text config (e.g. gemma-4-26B-A4B-it, gemma-4-31B-it) require a vision-aware attention mask that makes tokens inside the same vision group visible to each other bidirectionally. HF's `Gemma4Model.forward` builds this mask via `create_causal_mask_mapping`. The MoE backend `Gemma4MoETextModelBackend.forward` was always building plain `create_causal_mask` + `create_sliding_window_causal_mask` regardless of the config flag. For `gemma-4-26B-A4B-it` this makes the MoE forward numerically diverge from HF on multimodal inputs (vision token logprobs can differ by 20+ in log-space), and increases `train/gen_kl_error` by roughly an order of magnitude during GRPO training (~0.01 vs ~0.001 on text-only). Fix: - Accept `mm_token_type_ids` and `pixel_values` in `Gemma4MoETextModelBackend.forward`. - When `config.use_bidirectional_attention == "vision"`, call HF's `create_causal_mask_mapping` (matches `Gemma4Model.forward`). Otherwise keep the existing plain causal-mask path. - Plumb `mm_token_type_ids` / `pixel_values` from `Gemma4ForConditionalGeneration.forward` down to the text backend. Measured impact on gemma-4-26B-A4B-it multimodal forward (HF as ground truth, single synthetic image, 341-token sequence): metric before after (expected) HF vs Automodel gen_kl 0.034 ~0.01 (FSDP noise floor) HF vs vLLM gen_kl 0.092 0.092 (unchanged) Signed-off-by: jQizhang <larkz@nvidia.com> Signed-off-by: NeMo Bot <nemo-bot@nvidia.com>
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/ok to test 813b0d3 |
svcnvidia-nemo-ci
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adil-a,
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beep boop [🤖]: Hi @jQizhang 👋,