Incremental Network Quantization

A PyTorch implementation of "Incremental Network Quantization: Towards Lossless CNNs with Low-Precision Weights"

@inproceedings{zhou2017,
title={Incremental Network Quantization: Towards Lossless CNNs with Low-Precision Weights},
author={Aojun Zhou, Anbang Yao, Yiwen Guo, Lin Xu, Yurong Chen},
booktitle={International Conference on Learning Representations,ICLR2017},
year={2017},
}

[Paper]

Official Caffe implementation is available [here] (Code in this repo is based on the paper and not on the official Caffe implementation)

Installation

The code is implemented in Python 3.7 and PyTorch 1.1

pip install -e .

Usage

inq.SGD(...) implements SGD that only updates weights according to the weight partitioning scheme of INQ.

inq.INQScheduler(...) handles the the weight partitioning and group-wise quantization stages of the incremental network quantization procedure.

reset_lr_scheduler(...) resets the learning rate scheduler.

Examples

The INQ training procedure looks like the following:

optimizer = inq.SGD(...)
scheduler = torch.optim.lr_scheduler.StepLR(optimizer, ...)
inq_scheduler = inq.INQScheduler(optimizer, [0.5, 0.75, 0.82, 1.0], strategy="pruning")
for inq_step in range(3): # Iteration for accumulated quantized weights of 50% 75% and 82% 
    inq.reset_lr_scheduler(scheduler)
    inq_scheduler.step()
    for epoch in range(5):
        scheduler.step()
        train(...)
inq_scheduler.step() # quantize all weights, further training is useless
validate(...)

examples/imagenet_quantized.py is a modified version of the official PyTorch imagenet example. Using this example you can quantize a pretrained model on imagenet. Compare the file to the original example to see the differences.

Results

Results using this code differ slightly from the results reported in the paper.