Qwen3.5-397B-A17B-REAP-28-NVFP4

edit: with vllm, use --language-model-only , have not figured this one out yet.

Qwen3.5-397B-A17B — REAP 28% Pruned, NVFP4

A personal experiment in aggressive MoE pruning. The goal: fit Qwen3.5-397B on 2× 96GB Blackwell GPUs with usable KV cache (~90K tokens), without losing quality.

What this is

28% of experts removed using REAP (Routing-Expert Activation Pruning) with a saliency × activation-count ordering, then quantized to NVFP4 using llm-compressor. Final size: ~164GB.

Pruning is heterogeneous — each layer retains a different number of experts based on global importance ranking. Early layers (which carry more redundancy) are pruned more aggressively; late layers are barely touched. This maximizes quality retention for a given size budget.

Benchmark results (non-thinking, lm-eval-harness)

28% fewer experts, 30%+ smaller on disk, and benchmark scores within noise of the full model.

Requirements

• vLLM ≥ 0.16.1 (nightly dev builds from the cu130 index work)
• Transformers ≥ 5.3

vLLM patches required

This model uses variable expert counts per layer (not a fixed number), which stock vLLM doesn't support yet. Two files need patching — see the patches/ directory for detailed instructions:

1. qwen3_next.py — read per-layer expert count instead of assuming a single global value
2. qwen3_5.py — infer expert count from tensor shape during weight loading

Patches were tested on vLLM 0.16.1rc1.dev188 (nightly cu130).

Details

• Base model: Qwen3.5-397B-A17B
• Pruning: REAP with 1,188 curated calibration samples, saliency × count global ordering
• Quantization: NVFP4 (FP4 E2M1, group size 16, duo scaling)
• Target hardware: 2× RTX PRO 6000