Incremental Network Quantization: Towards Lossless CNNs with Low-precision Weights
This paper presents incremental network quantization (INQ), a novel method, targeting to efficiently convert any pre-trained full-precision convolutional neural network (CNN) model into a low-precision version whose weights are constrained to be either powers of two or zero. Unlike existing methods which are struggled in noticeable accuracy loss, our INQ has the potential to resolve this issue, as benefiting from two innovations. On one hand, we introduce three interdependent operations, namely weight partition, group-wise quantization and re-training. A well-proven measure is employed to divide the weights in each layer of a pre-trained CNN model into two disjoint groups. The weights in the first group are responsible to form a low-precision base, thus they are quantized by a variable-length encoding method. The weights in the other group are responsible to compensate for the accuracy loss from the quantization, thus they are the ones to be re-trained. On the other hand, these three operations are repeated on the latest re-trained group in an iterative manner until all the weights are converted into low-precision ones, acting as an incremental network quantization and accuracy enhancement procedure. Extensive experiments on the ImageNet classification task using almost all known deep CNN architectures including AlexNet, VGG-16, GoogleNet and ResNets well testify the efficacy of the proposed method. Specifically, at 5-bit quantization (a variable-length encoding: 1 bit for representing zero value, and the remaining 4 bits represent at most 16 different values for the powers of two), our models have improved accuracy than the 32-bit floating-point references. Taking ResNet-18 as an example, we further show that our quantized models with 4-bit, 3-bit and 2-bit ternary weights have improved or very similar accuracy against its 32-bit floating-point baseline. Besides, impressive results with the combination of network pruning and INQ are also reported. We believe that our method sheds new insights on how to make deep CNNs to be applicable on mobile or embedded devices. The code will be made publicly available.
There is a great deal of ongoing interest in compressing neural network models. One line of work has focused on using low-precision representations of the model weights, even down to 1 or 2 bits. However, so far these approaches have been accompanied by a significant impact on accuracy. The paper proposes an iterative quantization scheme, in which the network weights are quantized in stages---the largest weights (in absolute value) are quantized and fixed, while unquantized weights can adapt to compensate for any resulting error. The experimental results show this is extremely effective, yielding models with 4 bit or 3 bit weights with essentially no reduction in accuracy. While at 2 bits the accuracy decreases slightly, the results are substantially better than those achieved with other quantization approaches. Overall this paper is clear, the technique is as far as I am aware novel, the experiments are thorough and the results are very compelling, so I recommend acceptance. The paper could use another second pass for writing style and grammar. Also, the description of the pruning-inspired partitioning strategy could be clarified somewhat... e.g., the chosen splitting ratio of 50% only seems to be referenced in a figure caption and not the main text.
You are a member of the scientific community tasked with peer review. Review the following paper title and abstract.
### Title + Abstract
Incremental Network Quantization: Towards Lossless CNNs with Low-precision Weights
This paper presents incremental network quantization (INQ), a novel method, targeting to efficiently convert any pre-trained full-precision convolutional neural network (CNN) model into a low-precision version whose weights are constrained to be either powers of two or zero. Unlike existing methods which are struggled in noticeable accuracy loss, our INQ has the potential to resolve this issue, as benefiting from two innovations. On one hand, we introduce three interdependent operations, namely weight partition, group-wise quantization and re-training. A well-proven measure is employed to divide the weights in each layer of a pre-trained CNN model into two disjoint groups. The weights in the first group are responsible to form a low-precision base, thus they are quantized by a variable-length encoding method. The weights in the other group are responsible to compensate for the accuracy loss from the quantization, thus they are the ones to be re-trained. On the other hand, these three operations are repeated on the latest re-trained group in an iterative manner until all the weights are converted into low-precision ones, acting as an incremental network quantization and accuracy enhancement procedure. Extensive experiments on the ImageNet classification task using almost all known deep CNN architectures including AlexNet, VGG-16, GoogleNet and ResNets well testify the efficacy of the proposed method. Specifically, at 5-bit quantization (a variable-length encoding: 1 bit for representing zero value, and the remaining 4 bits represent at most 16 different values for the powers of two), our models have improved accuracy than the 32-bit floating-point references. Taking ResNet-18 as an example, we further show that our quantized models with 4-bit, 3-bit and 2-bit ternary weights have improved or very similar accuracy against its 32-bit floating-point baseline. Besides, impressive results with the combination of network pruning and INQ are also reported. We believe that our method sheds new insights on how to make deep CNNs to be applicable on mobile or embedded devices. The code will be made publicly available.
user
<think>Okay, to do a decent peer review, I should start with summarizing what the work is about. This includes novelty, contributions, clarity, and impact. I might include suggestions to issues that I find critical to the usefulness of the work. Starting with novelty, there are different types of novelty. The first aspect of novelty is scope and scale. Is the work covering a broader perspective than previous works? The second aspect is methodology. Is the proposed methodology novel compared to previous methods? Do they provide any significant advantage over previous methodologies? The third aspect is results. Are the results different compared previous work? Does this lead to any novel theories or an extension of current theories? Next is clarity, I will be reading the work in depth and analyze if any sentences can be potentially ambiguous or misleading. If any sentences are ambiguous, I will state them and give a suggestion on how to rephrase such sentence or how to make more clear to the audience. Lastly, impact is important. I will attempt to predict how such work will impact the scientific community. This might include the applications of such work and how the work might transform the way we study a certain topic. Finally, I will might only mention issues that are critical. This is to keep the review as concise and helpful as possible.</think>



There is a great deal of ongoing interest in compressing neural network models. One line of work has focused on using low-precision representations of the model weights, even down to 1 or 2 bits. However, so far these approaches have been accompanied by a significant impact on accuracy. The paper proposes an iterative quantization scheme, in which the network weights are quantized in stages---the largest weights (in absolute value) are quantized and fixed, while unquantized weights can adapt to compensate for any resulting error. The experimental results show this is extremely effective, yielding models with 4 bit or 3 bit weights with essentially no reduction in accuracy. While at 2 bits the accuracy decreases slightly, the results are substantially better than those achieved with other quantization approaches. Overall this paper is clear, the technique is as far as I am aware novel, the experiments are thorough and the results are very compelling, so I recommend acceptance. The paper could use another second pass for writing style and grammar. Also, the description of the pruning-inspired partitioning strategy could be clarified somewhat... e.g., the chosen splitting ratio of 50% only seems to be referenced in a figure caption and not the main text.
assistant
There is a great deal of ongoing interest in compressing neural network models. One line of work has focused on using low-precision representations of the model weights, even down to 1 or 2 bits. However, so far these approaches have been accompanied by a significant impact on accuracy. The paper proposes an iterative quantization scheme, in which the network weights are quantized in stages---the largest weights (in absolute value) are quantized and fixed, while unquantized weights can adapt to compensate for any resulting error. The experimental results show this is extremely effective, yielding models with 4 bit or 3 bit weights with essentially no reduction in accuracy. While at 2 bits the accuracy decreases slightly, the results are substantially better than those achieved with other quantization approaches. Overall this paper is clear, the technique is as far as I am aware novel, the experiments are thorough and the results are very compelling, so I recommend acceptance. The paper could use another second pass for writing style and grammar. Also, the description of the pruning-inspired partitioning strategy could be clarified somewhat... e.g., the chosen splitting ratio of 50% only seems to be referenced in a figure caption and not the main text.