Quantizing KV Cache for DeepSeek V4 Flash Significantly Degrades Quality
erazortt · reddit · 2026-08-03
A developer tested the quality impact of quantizing the KV Cache from BF16 to Q8 on the DeepSeek V4 Flash (DS4F) model. The results show a significant performance degradation, advising against KV quantization for this specific model.
Core Data Comparison:
- DS4F: Post-quantization Perplexity (PPL) increased, KL Divergence (KLD) spiked significantly, and Top-P probability consistency dropped to 87.189%.
- Qwen 397B: In contrast, Qwen 397B showed minimal KLD under the same quantization conditions, maintaining a 97.929% Top-P consistency.
This indicates that unlike some highly tolerant models, DeepSeek V4 Flash is highly sensitive to KV Cache quantization, and forcing it will lead to noticeable quality loss.
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