SPIQ: Data-Free Per-Channel Static Input Quantization

TL;DR

SPIQ introduces a data-free, per-channel static input quantization method that achieves accuracy comparable to dynamic methods while maintaining static inference speed, improving efficiency in neural network deployment.

Contribution

The paper presents SPIQ, a novel static input quantization scheme that rivals dynamic methods in accuracy without incurring additional inference costs.

Findings

Achieves accuracy comparable to dynamic quantization methods.

Significantly outperforms existing static quantization techniques.

Effective across multiple computer vision benchmarks.

Abstract

Computationally expensive neural networks are ubiquitous in computer vision and solutions for efficient inference have drawn a growing attention in the machine learning community. Examples of such solutions comprise quantization, i.e. converting the processing values (weights and inputs) from floating point into integers e.g. int8 or int4. Concurrently, the rise of privacy concerns motivated the study of less invasive acceleration methods, such as data-free quantization of pre-trained models weights and activations. Previous approaches either exploit statistical information to deduce scalar ranges and scaling factors for the activations in a static manner, or dynamically adapt this range on-the-fly for each input of each layers (also referred to as activations): the latter generally being more accurate at the expanse of significantly slower inference. In this work, we argue that static input quantization can reach the accuracy levels of dynamic methods by means of a per-channel input quantization scheme that allows one to more finely preserve cross-channel dynamics. We show through a thorough empirical evaluation on multiple computer vision problems (e.g. ImageNet classification, Pascal VOC object detection as well as CityScapes semantic segmentation) that the proposed method, dubbed SPIQ, achieves accuracies rivalling dynamic approaches with static-level inference speed, significantly outperforming state-of-the-art quantization methods on every benchmark.