Using real task success rather than calibration statistics to allocate bit widths got vision-language-action models running at roughly 4-bit weights and under 6-bit activations
AspireAI community · arXiv
Post-training quantization of vision-language-action models has typically assigned bit widths using sensitivity estimates from calibration data, which ignores that the effect of quantizing one component depends on the precision of others and that closed-loop task success is the real target. QbD-VLA instead uses task success from short closed-loop evaluations to assign weight and activation bit widths while accounting for interactions between components, across four VLA models and all four LIBERO suites, reaching strong task performance at average precisions of approximately 4 bits for weights and fewer than 6 bits for activations. The honest limitation is in the paper's own results: the gain over uniform quantization is small on SIMPLER, and on a Franka Research 3 arm the simulation-selected allocations showed no detected success-rate loss for X-VLA but failed for pi-0.5, which the authors read as a need for real-world evaluation before deployment.
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