Variance-based Gradient Compression for Efficient Distributed Deep Learning
Due to the substantial computational cost, training state-of-the-art deep neural networks for large-scale datasets often requires distributed training using multiple computation workers. However, by nature, workers need to frequently communicate gradients, causing severe bottlenecks, especially on lower bandwidth connections. A few methods have been proposed to compress gradient for efficient communication, but they either suffer a low compression ratio or significantly harm the resulting model accuracy, particularly when applied to convolutional neural networks. To address these issues, we propose a method to reduce the communication overhead of distributed deep learning. Our key observation is that gradient updates can be delayed until an unambiguous (high amplitude, low variance) gradient has been calculated. We also present an efficient algorithm to compute the variance and prove that it can be obtained with negligible additional cost. We experimentally show that our method can achieve very high compression ratio while maintaining the result model accuracy. We also analyze the efficiency using computation and communication cost models and provide the evidence that this method enables distributed deep learning for many scenarios with commodity environments.
 The authors propose a new gradient compression method for efficient distributed training of neural networks. The authors propose a novel way of measuring ambiguity based on the variance of the gradients. In the experiment, the proposed method shows no or slight degradation of accuracy with big savings in communication cost. The proposed method can easily be combined with other existing method, i.e., Storm (2015), based on the absolute value of the gradient and shows further efficiency. The paper is well written: clear and easy to understand. The proposed method is simple yet powerful. Particularly, I found it interesting to re-evaluate the variance with (virtually) increasing larger batch size. The performance shown in the experiments is also impressive. I found it would have also been interesting and helpful to define and show a new metric that incorporates both accuracy and compression rate into a single metric, e.g., how much accuracy is lost (or gained) per compression rate relatively to the baseline of no compression. With this metric, the comparison would be easier and more intuitive.
You are a member of the scientific community tasked with peer review. Review the following paper title and abstract.
### Title + Abstract
Variance-based Gradient Compression for Efficient Distributed Deep Learning
Due to the substantial computational cost, training state-of-the-art deep neural networks for large-scale datasets often requires distributed training using multiple computation workers. However, by nature, workers need to frequently communicate gradients, causing severe bottlenecks, especially on lower bandwidth connections. A few methods have been proposed to compress gradient for efficient communication, but they either suffer a low compression ratio or significantly harm the resulting model accuracy, particularly when applied to convolutional neural networks. To address these issues, we propose a method to reduce the communication overhead of distributed deep learning. Our key observation is that gradient updates can be delayed until an unambiguous (high amplitude, low variance) gradient has been calculated. We also present an efficient algorithm to compute the variance and prove that it can be obtained with negligible additional cost. We experimentally show that our method can achieve very high compression ratio while maintaining the result model accuracy. We also analyze the efficiency using computation and communication cost models and provide the evidence that this method enables distributed deep learning for many scenarios with commodity environments.
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>



 The authors propose a new gradient compression method for efficient distributed training of neural networks. The authors propose a novel way of measuring ambiguity based on the variance of the gradients. In the experiment, the proposed method shows no or slight degradation of accuracy with big savings in communication cost. The proposed method can easily be combined with other existing method, i.e., Storm (2015), based on the absolute value of the gradient and shows further efficiency. The paper is well written: clear and easy to understand. The proposed method is simple yet powerful. Particularly, I found it interesting to re-evaluate the variance with (virtually) increasing larger batch size. The performance shown in the experiments is also impressive. I found it would have also been interesting and helpful to define and show a new metric that incorporates both accuracy and compression rate into a single metric, e.g., how much accuracy is lost (or gained) per compression rate relatively to the baseline of no compression. With this metric, the comparison would be easier and more intuitive.
assistant
 The authors propose a new gradient compression method for efficient distributed training of neural networks. The authors propose a novel way of measuring ambiguity based on the variance of the gradients. In the experiment, the proposed method shows no or slight degradation of accuracy with big savings in communication cost. The proposed method can easily be combined with other existing method, i.e., Storm (2015), based on the absolute value of the gradient and shows further efficiency. The paper is well written: clear and easy to understand. The proposed method is simple yet powerful. Particularly, I found it interesting to re-evaluate the variance with (virtually) increasing larger batch size. The performance shown in the experiments is also impressive. I found it would have also been interesting and helpful to define and show a new metric that incorporates both accuracy and compression rate into a single metric, e.g., how much accuracy is lost (or gained) per compression rate relatively to the baseline of no compression. With this metric, the comparison would be easier and more intuitive.