[WIP] NVFP4 Emulation

[mgoin]

Not correct yet

python -c "from vllm import LLM;out = LLM('nvidia/Llama-3.3-70B-Instruct-FP4', quantization='nvfp4', max_model_len=2048, enforce_eager=True).generate('Hi my name is');print(out)"

Processed prompts: 100%|███████████| 1/1 [00:35<00:00, 35.66s/it, est. speed input: 0.14 toks/s, output: 0.45 toks/s]
[RequestOutput(request_id=0, prompt='Hi my name is', prompt_token_ids=[128000, 13347, 856, 836, 374], encoder_prompt=None, encoder_prompt_token_ids=None, prompt_logprobs=None, outputs=[CompletionOutput(index=0, text='!!!!!!!!!!!!!!!!', token_ids=[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], cumulative_logprob=None, logprobs=None, finish_reason=length, stop_reason=None)], finished=True, metrics=None, lora_request=None, num_cached_tokens=None, multi_modal_placeholders={})]

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[dsikka]

@mgoin
My branch with fixes for the weight dequant: #59
Sitll looking at activations. Seemed like we were getting gibberish even wth activation quantization turned off.