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Add measured quantization-quality comparison vs mxfp4

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  1. README.md +18 -1
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@@ -105,6 +105,23 @@ print(generate(model, processor, prompt, ["your_image.jpg"], max_tokens=512, ver
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  Group size 64, `affine` mode. The vision tower is left unquantized (mlx-vlm's default for multimodal projector/patch-embed modules), so the size delta between tiers comes from the language model.
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  ## Sampling
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  DavidAU's notes for this model, which carry over:
@@ -131,7 +148,7 @@ These are not measurements of these MLX repos — treat them as characterising t
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  ## Conversion tooling
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- Scripts and the provenance proof: [github.com/PipeNetwork/defiant-fable-mlx](https://github.com/PipeNetwork/defiant-fable-mlx)
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  ## License
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  Group size 64, `affine` mode. The vision tower is left unquantized (mlx-vlm's default for multimodal projector/patch-embed modules), so the size delta between tiers comes from the language model.
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+ ## Measured quantization quality
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+
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+ Against the bf16 reference these were converted from — 65,536 tokens of wikitext-2 test
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+ at 1024 context, identical token ids through mlx-lm, on an M3 Ultra:
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+
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+ | model | ppl | Δppl | KL(bf16‖quant) | top-1 vs bf16 | decode |
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+ |---|---|---|---|---|---|
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+ | bf16 reference | 8.1273 | — | — | — | 39.0 t/s |
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+ | **this 4bit** (affine, group 64) | **8.5816** | **+5.59%** | **0.0733** | **87.06%** | 109.9 t/s |
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+ | [nightmedia mxfp4](https://huggingface.co/nightmedia/Qwen3.5-9B-DS9-USS-Defiant-mxfp4-mlx) (group 32) | 8.9443 | +10.05% | 0.1133 | 82.34% | 114.4 t/s |
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+
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+ The 4bit tier loses about half the perplexity that MXFP4 does and stays measurably closer
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+ to the original distribution, at the cost of 4.5 vs 4.25 bits/weight (~6% more storage)
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+ and ~4% slower decode. Both are quantizations of the same weights, so this compares the
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+ quantization scheme only. Reproduce with
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+ [`bench.py`](https://github.com/PipeNetwork/defiant-fable-mlx).
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+
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  ## Sampling
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  DavidAU's notes for this model, which carry over:
 
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  ## Conversion tooling
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+ Scripts, benchmark and the provenance proof: [github.com/PipeNetwork/defiant-fable-mlx](https://github.com/PipeNetwork/defiant-fable-mlx)
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  ## License
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