Qwen3-30B-A3B-NVFP4-RTN

NVFP4 (4-bit weights and activations) quantization of Qwen/Qwen3-30B-A3B, produced with llm-compressor using a round-to-nearest oneshot over 1,024 calibration samples. 18.11 GB on disk against the 56.89 GB bf16 original, a 3.14x reduction.

This is the cheap half of a deliberate pair. ThakiCloud/Qwen3-30B-A3B-NVFP4-GPTQ is the identical model at the identical bit width and file size, built with GPTQ instead. Both are published so the trade is visible rather than asserted.

Quality (measured, not inherited)

Single B200, vLLM 0.27.1, lm-eval 0.4.12, full sets, no --limit. MMLU n=14,042 (loglikelihood); GSM8K-CoT n=1,319, 8-shot (generative).

This build loses about 1pp of MMLU (z = −2.2, borderline significant). The GPTQ sibling does not (−0.36pp, z = −0.8). GPTQ costs 4.5x the quantization time, and that 1pp is what it buys. Both timings come from quantize_meta.json, which ships in this repo. For a lot of deployments 1pp of MMLU is not worth 5.1 extra GPU-hours; for some it is. The pair exists so that is your call and not ours.

This build reproduces RedHatAI/Qwen3-30B-A3B-NVFP4 to within 0.01pp MMLU (0.7676 vs 0.7675), which is how we established that their NVFP4 is RTN and not GPTQ. If you were choosing between this and theirs on quality, they are the same checkpoint in every way we can measure; theirs is 1.23 GB smaller.

We do not claim quantization improves math. GSM8K comes out above bf16 for every 4-bit build in the table, consistently in sign, but z runs 1.1 to 2.1 over 1,319 generative samples and is not separable from sampling noise. The defensible claim is no measurable degradation on GSM8K.

Kernel path (the part most FP4 cards leave out)

A 4-bit checkpoint can hold NVFP4 weights and still expand them to bf16 for every matmul — slower than bf16, saving only memory. So we assert the kernel rather than assume it:

Using 'FLASHINFER_TRTLLM' NvFp4 MoE backend     # B200, no fallback warning

Verified on B200 (SM100) with vLLM 0.27.1, with no does not have native support for FP4 warning in the serving log.

⚠️ Blackwell only. On Hopper (H200/H100) vLLM falls back to weight-only Marlin emulation, which we measured at roughly 0.85x of bf16. NVFP4 is not a speed win on SM90; FP8 is the format that wins there.

Serving energy

Single B200, decode-dominant workload, GPU power only (host and cooling excluded):

⚠️ That run was not saturated (GPU utilisation 54 to 85 percent on 29-token prompts), so we withdraw its throughput claim and quote only the power gap, which is the defensible part.

Usage

vllm serve ThakiCloud/Qwen3-30B-A3B-NVFP4-RTN --max-model-len 8192

Check the serving log for the backend line above. MARLIN or a native-support warning means you are measuring emulation, not FP4.

Scope

One model, one recipe, one engine version, one GPU generation for the kernel claim. Quality was measured on MMLU and GSM8K only; code, multilingual and long-context behaviour are unevaluated and unclaimed.