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HiFloat4 needed its own calibration methods, and the resulting gap to BF16 lands under one percent

AspireAI community · arXiv
4-bit formats like MXFP4 and NVFP4 are spreading fast, and HiFloat4 is a newer block-floating-point format with a three-level scaling hierarchy and a wider dynamic range. Its problem is that the calibration methods built for integer formats like INT4 do not transfer, so the gap between quantized and full-precision accuracy does not close on their own. The authors adapt three well-known calibration approaches - HiGPTQ, HiAutoRound and HiFlatQuant - to the HiF4 format, and report that all three improve accuracy over direct conversion, narrowing the HiF4-to-BF16 gap to less than 1% and outperforming the state-of-the-art NVFP4 format across models and downstream tasks. These are the authors' own implementations, so the comparison against NVFP4 reflects their setup rather than a neutral benchmark.
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