UNIQ: Uniform Noise Injection for non-uniform Quantization of neural networks
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We present a novel method for training a neural network amenable to inference in low-precision arithmetic with quantized weights and activations. The training is performed in full precision with random noise injection emulating quantization noise. In order to circumvent the need to simulate realistic quantization noise distributions, the weight distributions are uniformized by a non-linear transformation, and uniform noise is injected. This procedure emulates a non-uniform k-quantile quantizer at inference time, which adapts to the specific distribution of the quantized parameters. As a by-product of injecting noise to weights, we find that activations can also be quantized to as low as 8-bit with only a minor accuracy degradation. The method achieves state-of-the-art results for training low-precision networks on ImageNet. In particular, we observe no degradation in accuracy for MobileNet and ResNet-18/34/50 on ImageNet with as low as 4-bit quantization of weights. Our solution achieves the state-of-the-art results in accuracy, in the low computational budget regime, compared to similar models.
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