b9911

ggml-org/llama.cppb9911Jul 8, 2026by github-actions[bot]

AI Summary

Implements fused matrix-vector quantization (MMVQ) post-scale operations specifically for NVIDIA FP4 (NVFP4) quantization on CUDA, resulting in performance improvements.

Key Highlights

  • Fuse MMVQ post-scale operations for NVFP4 quantization on CUDA
  • Add dense MMVQ fusion
  • Significant speedup on B4500 and DGX Spark hardware
  • Add tests for the new fusion ops

New Features

  • CUDA NVFP4 fusion optimization

Full Release Notes

<details open>

CUDA: Fuse MMVQ post-scale for NVFP4 (#24481)

* CUDA: Fuse MMVQ for NVFP4 and BS 1

TODO:
1. Add tests to test-backend-ops (did verify correctness manually for
   one model)
2. Reorder bias/scale once PRs for NVFP4 are merged/landed

* Add dense MMVQ fusion as well

Perf numbers on B4500. Note qwen35 is FP8->Q8
+ ./scripts/compare-llama-bench.py -b master -c osimons/nvfp4_fuse_mmvq --tool llama-bench -i llama-bench.sqlite
| Model                    | Test         |   t/s master |   t/s osimons/nvfp4_fuse_mmvq |   Speedup |
|:-------------------------|:-------------|-------------:|------------------------------:|----------:|
| qwen35moe 35B.A3B NVFP4  | tg128@d32768 |       150.15 |                        156.29 |      1.04 |
| qwen35moe 35B.A3B Q4_K_M | tg128@d32768 |       157.91 |                        157.64 |      1.00 |

Perf numbers on DGX Spark
+ ./scripts/compare-llama-bench.py -b master -c osimons/nvfp4_fuse_mmvq --tool llama-bench -i llama-bench.sqlite
| Model                    | Test         |   t/s master |   t/s osimons/nvfp4_fuse_mmvq |   Speedup |
|:-------------------------|:-------------|-------------:|------------------------------:|----------:|
| qwen35moe 35B.A3B NVFP4  | tg128@d32768 |        58.31 |                         59.69 |      1.02 |
| qwen35moe 35B.A3B Q4_K_M | tg128@d32768 |        54.94 |                         54.79 |      1.00 |

* Add tests for the added fusion ops

* Cleanup test-backend-ops

* Cleanup ggml-cuda/mmvq

1. Unrestrict post-scale fusion
2. Rename names accordingly
3. Remove env variable to disable fusion

* Merge old mul_mat patterns into the lane-based approach

* Enable fusion for MoE in shared MMVQ

* Restrict scale_view_nodes, enroll MM + ADD into lane-matcher

* Refactor mmvq loads, still does not help non-nvfp4 kernels

* Restrict scale-fusion to NVFP4

This is necessary, as the prolog is quite heavy in GEMV for some
quants/model configs, leading to net perf regression.
We should really be looking to refactor this such that ratio of
prologue/hot-loop/epilogue is better on the hot-loop
front:

+ ./scripts/compare-llama-bench.py -b master -c c1b9381d327e063cc846b46b59708444b66dc4d8 --tool llama-bench -i llama-bench.sqlite
| CPU                         | Model                    | Test         |   t/s master |   t/s c1b9381d3 |   Speedup |
|:----------------------------|:-------------------------|:-------------|-------------:|----------------:|----------:|
| INTEL(R) XEON(R) GOLD 6542Y | gemma4 26B.A4B NVFP4     | tg128@d32768 |       151.70 |          154.32 |      1.02 |
| INTEL(R) XEON(R) GOLD 6542Y | gemma4 26B.A4B Q4_K_M    | tg128@d32768 |       187.95 |          185.73 |      0.99 |
| INTEL(R) XEON(R) GOLD 6542Y | gpt-oss 20B MXFP4 MoE    | tg128@d32768 |       304.62 |          300.69 |      0.99 |
| INTEL(R) XEON(R) GOLD 6542Y | qwen35moe 35B.A3B NVFP4  | tg128@d32768 |       193.72 |          211.99 |      1.09 |
| INTEL(R) XEON(R) GOLD 6542Y | qwen35moe 35B.A3B Q4_K_M | tg128@d32768 |       217.76 |          218.15 |      1.00

* Reorder scale & bias-add to adhere to #24331

* Restrict lane scale to NVFP4

Don't need to test unfused combinations

* Cleanup

* Merge single-lane mm-fusion helpers

* Refactor and clean-up host-side fusion logic

* Move gate_bias and scale into the same active-thread guard

Latest perf numbers:
B6000

build: 5b7d9f272 (9578)
+ ./scripts/compare-llama-bench.py -b master -c osimons/nvfp4_fuse_mmvq --tool llama-bench -i llama-bench.sqlite
| CPU                         | Model                    | Test         |   t/s master |   t/s osimons/nvfp4_fuse_mmvq |   Speedup |
|:----------------------------|:-------------------------|:-------------|-------------:|------------------------------:|----------:|
| INTEL(R) XEON(R) GOLD 6542Y | gemma4 26B.A4B NVFP4     | tg128@d32768 |       151.79 |                        154.10 |      1.02 |
| INTEL(R) XEON(R) GOLD 6542Y | gemma4 26B.A4B Q4_K_M    | tg128@d32768 |       187.90 |                        187.27 |      1.00 |
| INTEL(R) XEON(R) GOLD 6542Y | gpt-oss 20B MXFP4 MoE    | tg128@d32768 |       303.77 |                        306.56 |      1.01 |
| INTEL(R) XEON(R) GOLD 6542Y | qwen35moe 35B.A3B NVFP4  | tg128@d32768 |       193.41 |                        207.99 |      1.08 |
| INTEL(R) XEON(R) GOLD 6542Y | qwen35moe 35B.A3B Q4_K_M | tg128@d32768 |       217.60 |                        218.58 |      1.00 |

DGX Spark

build: 5b7d9f272 (9578)
+ ./scripts/compare-llama-bench.py -b master -c osimons/nvfp4_fuse_mmvq --tool llama-bench -i llama-bench.sqlite
| CPU   | Model                    | Test         |   t/s master |   t/s osimons/nvfp4_fuse_mmvq |   Speedup |
|:------|:-------------------------|:-------------|-------------:|------------------------------:|----------:|
| CPU   | gemma4 26B.A4B NVFP4     | tg128@d32768 |        34.61 |                         34.84 |      1.01 |
| CPU   | gemma4 26B.A4B Q4_K_M    | tg128@d32768 |        46.95 |                         46.90 |      1.00 |
| CPU   | gpt-oss 20B MXFP4 MoE    | tg128@d32768 |        64.84 |                         64.62 |      1.00 |
| CPU   | qwen35moe 35B.A3B NVFP4  | tg128@d32768 |        59.63 |                         60.72 |      1.02 |
| CPU   | qwen35moe 35B.A3B Q4_K_M | tg128@d32768 |        56.53 |                         56.55 |      1.00 |

PPL values for 5 chunks:
this PR

model                                                                                                       mode             ppl         uncertainty  log
/mnt/share/gguf/unsloth/Qwen3.6-35B-A3B-GGUF/Qwen3.6-35B-A3B-UD-Q4_K_M.gguf                                 fusion_enabled   5.2892      0.35389      ppl-value-checks/Qwen3.6-35B-A3B-UD-Q4_K_M.fusion_enabled.log
/mnt/share/gguf/unsloth/Qwen3.6-35B-A3B-GGUF/Qwen3.6-35B-A3B-UD-Q4_K_M.gguf                                 fusion_disabled  5.2742      0.35215      ppl-value-checks/Qwen3.6-35B-A3B-UD-Q4_K_M.fusion_disabled.log
/mnt/share/gguf/nvidia/Qwen3.6-35B-A3B-2.06GB-per-token-CT/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.gguf  fusion_enabled   5.4487      0.36866      ppl-value-checks/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.fusion_enabled.log
/mnt/share/gguf/nvidia/Qwen3.6-35B-A3B-2.06GB-per-token-CT/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.gguf  fusion_disabled  5.4403      0.36782      ppl-value-checks/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.fusion_disabled.log
/mnt/share/gguf/nvidia/Gemma-4-26B-A4B-NVFP4/Gemma-4-26B-A4B-NVFP4_fp8_q8.gguf                              fusion_enabled   17342.4348  3703.13932   ppl-value-checks/Gemma-4-26B-A4B-NVFP4_fp8_q8.fusion_enabled.log
/mnt/share/gguf/nvidia/Gemma-4-26B-A4B-NVFP4/Gemma-4-26B-A4B-NVFP4_fp8_q8.gguf                              fusion_disabled  18627.0624  3998.42475   ppl-value-checks/Gemma-4-26B-A4B-NVFP4_fp8_q8.fusion_disabled.log
/mnt/share/gguf/ggml-org/gpt-oss-20b-GGUF/gpt-oss-20b-mxfp4.gguf                                            fusion_enabled   363.8913    33.14007     ppl-value-checks/gpt-oss-20b-mxfp4.fusion_enabled.log
/mnt/share/gguf/ggml-org/gpt-oss-20b-GGUF/gpt-oss-20b-mxfp4.gguf                                            fusion_disabled  363.8913    33.14007     ppl-value-checks/gpt-oss-20b-mxfp4.fusion_disabled.log
/mnt/share/gguf/unsloth/gemma-4-26B-A4B-it-GGUF/gemma-4-26B-A4B-it-UD-Q4_K_XL.gguf                          fusion_enabled   17330.3926  3716.70472   ppl-value-checks/gemma-4-26B-A4B-it-UD-Q4_K_XL.fusion_enabled.log
/mnt/share/gguf/unsloth/gemma-4-26B-A4B-it-GGUF/gemma-4-26B-A4B-it-UD-Q4_K_XL.gguf                          fusion_disabled  17933.9524  3883.17066   ppl-value-checks/gemma-4-26B-A4B-it-UD-Q4_K_XL.fusion_disabled.log

master:
summary: ppl-value-checks/summary.tsv
model                                                                                                       mode             ppl         uncertainty  log
/mnt/share/gguf/unsloth/Qwen3.6-35B-A3B-GGUF/Qwen3.6-35B-A3B-UD-Q4_K_M.gguf                                 fusion_enabled   5.2892      0.35389      ppl-value-checks/Qwen3.6-35B-A3B-UD-Q4_K_M.fusion_enabled.log
/mnt/share/gguf/unsloth/Qwen3.6-35B-A3B-GGUF/Qwen3.6-35B-A3B-UD-Q4_K_M.gguf                                 fusion_disabled  5.2742      0.35215      ppl-value-checks/Qwen3.6-35B-A3B-UD-Q4_K_M.fusion_disabled.log
/mnt/share/gguf/nvidia/Qwen3.6-35B-A3B-2.06GB-per-token-CT/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.gguf  fusion_enabled   5.4487      0.36866      ppl-value-checks/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.fusion_enabled.log
/mnt/share/gguf/nvidia/Qwen3.6-35B-A3B-2.06GB-per-token-CT/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.gguf  fusion_disabled  5.4403      0.36782      ppl-value-checks/Qwen3.6-35B-A3B-2.06GB-per-token-CT_fp8_q8.fusion_disabled.log
/mnt/share/gguf/nvidia/Gemma-4-26B-A4B-NVFP4/Gemma-4-26B-A4B-NVFP4_fp8_q8.gguf                              fusion_enabled   17342.4348  3703.13932   ppl-value-checks/Gemma-4-26B-A4B-NVFP4_fp8_q8.fusion_enabled.log
/mnt/share/gguf/nvidia/Gemma-4-26B-A4B-NVFP4/Gemma-4-26B-A4B-NVFP4_fp8_q8.gguf                              fusion_disabled  18627.0624  3998.42475   ppl-value-checks/Gemma-4-26B-A4B-NVFP4_fp8_q8.fusion_disabled.log
/mnt/share/gguf/ggml-org/gpt-oss-20b-GGUF/gpt-oss-20b-mxfp4.gguf                                            fusion_enabled   363.8913    33.14007     ppl-value-checks/gpt-oss-20b-mxfp4.fusion_enabled.log
/mnt/share/gguf/ggml-org/gpt-oss-20b-GGUF/gpt-oss-20b-mxfp4.gguf                                            fusion_disabled  363.8913    33.14007     ppl-value-checks/gpt-oss-20b-mxfp4.fusion_disabled.log
/mnt/share/gguf/unsloth/gemma-4-26B-A4B-it-GGUF/gemma-4-26B-A4B-it-UD-Q4_K_XL.gguf                          fusion_enabled   17330.3926  3716.70472   ppl-value-checks/gemma-4-26B-A4B-it-UD-Q4_K_XL.fusion_enabled.log
/mnt/share/gguf/unsloth/gemma-4-26B-A4B-it-GGUF/gemma-4-26B-A4B-it-UD-Q4_K_XL.gguf                          fusion_disabled  17933.9524  3883.17066   ppl-value-checks/gemma-4-26B-A4B-it-UD-Q4_K_XL.fusion_disabled.log

* Allow views to weights in ggml_can_fuse_subgraph

* Remove gate_first from test_mul_mat_vec_fusion

* Ditch lane-parsing approach in favor of hard-coded patterns

* Apply suggestions from code review

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* Rename ggml_is_constant_view_src to ggml_is_constant

* Finish renaming of 0905129e9d12e2bc6f16d6d3cc4e6b40606fc893

* Readd descriptive prints for fusion debugging

* Add weight-buffer pre-allocation to `test_case`

This is required so we correctly test fusion of NVFP4.

* Update ggml/src/ggml.c

Co-authored-by: Johannes Gäßler <johannesg@5d6.de>

* Add 2nd context for weights as suggested by @JohannesGaessler

This reflects more natural use of ggml compared to artifically
pre-allocating weights into the same context

* Exclude fused tests from gradient mode

I'm unsure of the current state, but naively every fusion pattern
should require its own backpropagation implementation. I don't see these
implemented for the CUDA backend, so we can disable tests to avoid
triggering GGML_ASSERT for

    ggml_tensor * build_graph(ggml_context * ctx) override {
        GGML_ASSERT(!use_weight_context());
        return build_graph(ctx, nullptr);
    }

* Apply suggestions from code review

Co-authored-by: Johannes Gäßler <johannesg@5d6.de>

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: Johannes Gäßler <johannesg@5d6.de>

</details>

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