ik_llama.cpp/docs/development/qwen3next_perf_diff_report.md

Qwen3Next Review and Benchmark Summary (ik_llama.cpp vs llama.cpp)

Date: 2026-02-08

Scope

This document captures:

• Current upstream PR alignment for Qwen3Next-related work.
• What is already strong in ik_llama.cpp and what still needs adjustment.
• Recommended runtime settings for this machine (single GPU target, long context).
• Final apples-to-apples benchmark matrix for ik_llama.cpp vs ../llama.cpp.

Upstream PR Check (as of 2026-02-08)

Reviewed PRs:

• https://github.com/ggml-org/llama.cpp/pull/18102 (open): Delta-Net CUDA op + integration.
• https://github.com/ggml-org/llama.cpp/pull/18792 (open): unified DeltaNet handling (src/models/delta.cpp).
• https://github.com/ggml-org/llama.cpp/pull/19375 (open, draft): Qwen3Next graph optimization in model builder.

Current alignment in ik_llama.cpp

Already present and/or functionally covered:

• CUDA DeltaNet op path exists in GGML (ggml/src/ggml-cuda/delta-net.cu).
• Solve-tri and backend op support are present for the fused path.
• Qwen3Next fused DeltaNet builder path exists (and is now runtime-toggleable via env).
• Existing ik optimizations remain available (-rtr, grouped/fused paths, no-offload-only-active-experts switches).

Not directly mirrored yet (by design divergence from mainline model layout):

• Mainline src/models/delta.cpp structure from PR #18792.
• Mainline src/models/qwen3next.cpp graph-form from PR #19375.

Required Adjustments (remaining)

1. Keep non-fused as the strict safety baseline, and use LLAMA_QWEN3NEXT_FUSED_DELTA=1 (prefill-only fused) as the practical acceleration mode.
2. Port selective graph-shape optimizations from PR #19375 into src/llama-build-context.cpp where they map cleanly (avoid blind copy due architectural divergence).
3. Add one dedicated Qwen3Next perf regression target in CI/dev docs (single-GPU 8k proxy + 65k fit sanity).
4. Investigate ik CPU Flash-Attn assertion path for Qwen3Next (iqk_fa_templates.h, S > 0) before enabling -fa 1 for CPU benchmark profiles.

Strong Points of ik_llama.cpp to Preserve

• More runtime controls than mainline for this workload (-rtr, backend toggles, MoE/OOAE controls).
• Strong CUDA path for this model family once offload routing is tuned (--n-cpu-moe thresholding).
• Better TG throughput than current mainline in matched CUDA and CPU tests on this host.

Best Runtime Configuration (this host)

Model: /models/qwen3-next-coder.gguf

Single-GPU long-context finding:

• -c 65536 on GPU0 (16 GB) requires at least --n-cpu-moe 47 to fit reliably.

8k sweep proxy (single GPU, tuned path):

• b=2048,ub=512 -> avg_tg ~27.9 tok/s
• b=3072,ub=768 -> avg_tg ~28.4 tok/s (best TG)
• b=4096,ub=1024 -> avg_tg ~26.9 tok/s

Recommended serving baseline:

• CUDA_VISIBLE_DEVICES=0
• -c 65536 -b 3072 -ub 768 -t 8 -fa on -ngl 999 --n-cpu-moe 47 -rtr

Final Benchmark Matrix (8k context proxy)

All four builds were benchmarked with matched parameters and explicit -mmp 0 for fairness.

Common args:

• -m /models/qwen3-next-coder.gguf -p 8192 -n 128 -b 3072 -ub 768 -t 8 -r 1
• CUDA runs: CUDA_VISIBLE_DEVICES=0 -fa 1 -ngl 999 --n-cpu-moe 47 -mmp 0
• CPU runs: -fa 0 -ngl 0 --n-cpu-moe 0 -mmp 0

Build	PP (tok/s)	TG (tok/s)
ik CUDA	204.614	28.979
mainline CUDA	184.521	22.012
ik CPU	49.795	12.681
mainline CPU	51.674	7.299

Relative (ik vs mainline):

• CUDA PP: +10.9%
• CUDA TG: +31.7%
• CPU PP: -3.6%
• CPU TG: +73.7%

Notes

• ik CPU benchmark with -fa 1 currently aborts for this model in iqk_fa_templates.h (GGML_ASSERT(S > 0)), so CPU matrix uses -fa 0 for both repos.
• ik benchmark JSON currently includes some non-JSON log lines in stdout around context creation; parsing should tolerate that.
• Fused DeltaNet mode mapping has been updated in code:
  • 0 / unset: non-fused
  • 1: fused only for n_tok > 1 (safe mode)
  • 2: fused on all token counts (experimental; decode-quality regression observed)
• Added manual regression runner for fused-mode safety checks:
  • scripts/qwen3next-fused-regression.sh
  • Example:
    • BIN=./build-qwen3next-fix/bin/llama-perplexity scripts/qwen3next-fused-regression.sh --model /models/qwen3-next-coder.gguf --ctx 2048 --decode-b 1 --decode-ub 1 --prefill-b 2048 --prefill-ub 512 --ngl 47 --n-cpu-moe 40
• Also integrated into the broader eval harness:
  • scripts/qwen3next-eval.sh --with-gpu --with-fused-regression ...
  • Results are surfaced in SUMMARY.md under IK Fused Delta Regression.
• Fused regression now enforces absolute non-fused sanity too:
  • mode0 decode/prefill PPL must stay below configurable thresholds (defaults: 10.0 / 10.0).