The mainstream approach for filter pruning is usually either to force a hard-coded importance estimation upon a computation-heavy pretrained model to select "important" filters, or to impose a hyperparameter-sensitive sparse constraint on the loss objective to regularize the network training. In this paper, we present a novel filter pruning method, dubbed dynamic-coded filter fusion (DCFF), to derive compact CNNs in a computation-economical and regularization-free manner for efficient image classification. Each filter in our DCFF is firstly given an inter-similarity distribution with a temperature parameter as a filter proxy, on top of which, a fresh Kullback-Leibler divergence based dynamic-coded criterion is proposed to evaluate the filter importance. In contrast to simply keeping high-score filters in other methods, we propose the concept of filter fusion, i.e., the weighted averages using the assigned proxies, as our preserved filters. We obtain a one-hot inter-similarity distribution as the temperature parameter approaches infinity. Thus, the relative importance of each filter can vary along with the training of the compact CNN, leading to dynamically changeable fused filters without both the dependency on the pretrained model and the introduction of sparse constraints. Extensive experiments on classification benchmarks demonstrate the superiority of our DCFF over the compared counterparts. For example, our DCFF derives a compact VGGNet-16 with only 72.77M FLOPs and 1.06M parameters while reaching top-1 accuracy of 93.47% on CIFAR-10. A compact ResNet-50 is obtained with 63.8% FLOPs and 58.6% parameter reductions, retaining 75.60% top-1 accuracy on ILSVRC-2012. Our code, narrower models and training logs are available at https://github.com/lmbxmu/DCFF.

Neural network pruning offers a promising prospect to facilitate deploying deep neural networks on resourcelimited devices. However, existing methods are still challenged by the training inefficiency and labor cost in pruning designs, due to missing theoretical guidance of non-salient network components. In this paper, we propose a novel filter pruning method by exploring the High Rank of feature maps (HRank). Our HRank is inspired by the discovery that the average rank of multiple feature maps generated by a single filter is always the same, regardless of the number of image batches CNNs receive. Based on HRank, we develop a method that is mathematically formulated to prune filters with low-rank feature maps. The principle behind our pruning is that low-rank feature maps contain less information, and thus pruned results can be easily reproduced. Besides, we experimentally show that weights with high-rank feature maps contain more important information, such that even when a portion is not updated, very little damage would be done to the model performance. Without introducing any additional constraints, HRank leads to significant improvements over the state-of-the-arts in terms of FLOPs and parameters reduction, with similar accuracies. For example, with ResNet-110, we achieve a 58.2%-FLOPs reduction by removing 59.2% of the parameters, with only a small loss of 0.14% in top-1 accuracy on CIFAR-10. With Res-50, we achieve a 43.8%-FLOPs reduction by removing 36.7% of the parameters, with only a loss of 1.17% in the top-1 accuracy on ImageNet. The codes can be available at https://github.com/lmbxmu/HRank.

过滤器修剪方法通过去除选定的过滤器来引入结构稀疏性，因此对于降低复杂性特别有效。先前的作品从验证较小规范的过滤器的角度从经验修剪网络中造成了较小的最终结果贡献。但是，此类标准已被证明对过滤器的分布敏感，并且由于修剪后的容量差距是固定的，因此准确性可能很难恢复。在本文中，我们提出了一种称为渐近软簇修剪（ASCP）的新型过滤器修剪方法，以根据过滤器的相似性来识别网络的冗余。首先通过聚类来区分来自参数过度的网络的每个过滤器，然后重建以手动将冗余引入其中。提出了一些聚类指南，以更好地保留特征提取能力。重建后，允许更新过滤器，以消除错误选择的效果。此外，还采用了各种修剪率的衰减策略来稳定修剪过程并改善最终性能。通过逐渐在每个群集中生成更相同的过滤器，ASCP可以通过通道添加操作将其删除，几乎没有准确性下降。 CIFAR-10和Imagenet数据集的广泛实验表明，与许多最新算法相比，我们的方法可以取得竞争性结果。

通过强迫连续重量的最多n非零，最近的N：M网络稀疏性因其两个有吸引力的优势而受到越来越多的关注：1）高稀疏性的有希望的表现。 2）对NVIDIA A100 GPU的显着加速。最近的研究需要昂贵的训练阶段或重型梯度计算。在本文中，我们表明N：M学习可以自然地将其描述为一个组合问题，该问题可以在有限的集合中寻找最佳组合候选者。由这种特征激励，我们以有效的分裂方式解决了n：m的稀疏性。首先，我们将重量向量分为$ c _ {\ text {m}}}^{\ text {n}} $组合s子集的固定大小N。然后，我们通过分配每个组合来征服组合问题，一个可学习的分数是共同优化了其关联权重。我们证明，引入的评分机制可以很好地模拟组合子集之间的相对重要性。通过逐渐去除低得分的子集，可以在正常训练阶段有效地优化N：M细粒稀疏性。全面的实验表明，我们的学习最佳组合（LBC）的表现始终如一，始终如一地比现成的N：m稀疏方法更好。我们的代码在\ url {https://github.com/zyxxmu/lbc}上发布。

This paper proposed a Soft Filter Pruning (SFP) method to accelerate the inference procedure of deep Convolutional Neural Networks (CNNs). Specifically, the proposed SFP enables the pruned filters to be updated when training the model after pruning. SFP has two advantages over previous works: (1) Larger model capacity. Updating previously pruned filters provides our approach with larger optimization space than fixing the filters to zero. Therefore, the network trained by our method has a larger model capacity to learn from the training data. (2) Less dependence on the pretrained model. Large capacity enables SFP to train from scratch and prune the model simultaneously. In contrast, previous filter pruning methods should be conducted on the basis of the pre-trained model to guarantee their performance. Empirically, SFP from scratch outperforms the previous filter pruning methods. Moreover, our approach has been demonstrated effective for many advanced CNN architectures. Notably, on ILSCRC-2012, SFP reduces more than 42% FLOPs on ResNet-101 with even 0.2% top-5 accuracy improvement, which has advanced the state-of-the-art. Code is publicly available on GitHub: https://github.com/he-y/softfilter-pruning

由于其实现的实际加速，过滤器修剪已广泛用于神经网络压缩。迄今为止，大多数现有滤波器修剪工作探索过滤器通过使用通道内信息的重要性。在本文中，从频道间透视开始，我们建议使用信道独立性进行有效的滤波器修剪，该指标测量不同特征映射之间的相关性。较少独立的特征映射被解释为包含较少有用的信息$ / $知识，因此可以修剪其相应的滤波器而不会影响模型容量。我们在过滤器修剪的背景下系统地调查了渠道独立性的量化度量，测量方案和敏感性$ / $可靠性。我们对各种数据集不同模型的评估结果显示了我们方法的卓越性能。值得注意的是，在CIFAR-10数据集上，我们的解决方案可以分别为基线Resnet-56和Resnet-110型号的0.75 \％$ 0.94 \％$ 0.94 \％。模型大小和拖鞋减少了42.8 \％$和$ 47.4 \％$（for Resnet-56）和48.3 \％$ 48.3 \％$ 52.1 \％$（for resnet-110）。在ImageNet DataSet上，我们的方法可以分别达到40.8 \％$ 44.8 \％$ 74.8 \％$ 0.15 \％$ 0.15 \％$ 0.15美元的准确性。该代码可在https://github.com/eclipsess/chip_neurivs2021上获得。

卷积神经网络（CNN）具有一定量的参数冗余，滤波器修剪旨在去除冗余滤波器，并提供在终端设备上应用CNN的可能性。但是，以前的作品更加注重设计了滤波器重要性的评估标准，然后缩短了具有固定修剪率的重要滤波器或固定数量，以减少卷积神经网络的冗余。它不考虑为每层预留有多少筛选器是最合理的选择。从这个角度来看，我们通过搜索适当的过滤器（SNF）来提出新的过滤器修剪方法。 SNF专用于搜索每层的最合理的保留过滤器，然后是具有特定标准的修剪过滤器。它可以根据不同的拖鞋定制最合适的网络结构。通过我们的方法进行过滤器修剪导致CIFAR-10的最先进（SOTA）精度，并在Imagenet ILSVRC-2012上实现了竞争性能。基于Reset-56网络，在Top-中增加了0.14％的增加0.14％ 1对CIFAR-10拖出的52.94％的精度为52.94％。在减少68.68％拖鞋时，CiFar-10上的修剪Resnet-110还提高了0.03％的1 0.03％的精度。对于Imagenet，我们将修剪速率设置为52.10％的拖鞋，前1个精度只有0.74％。该代码可以在https://github.com/pk-l/snf上获得。

We propose an efficient and unified framework, namely ThiNet, to simultaneously accelerate and compress CNN models in both training and inference stages. We focus on the filter level pruning, i.e., the whole filter would be discarded if it is less important. Our method does not change the original network structure, thus it can be perfectly supported by any off-the-shelf deep learning libraries. We formally establish filter pruning as an optimization problem, and reveal that we need to prune filters based on statistics information computed from its next layer, not the current layer, which differentiates ThiNet from existing methods. Experimental results demonstrate the effectiveness of this strategy, which has advanced the state-of-the-art. We also show the performance of ThiNet on ILSVRC-12 benchmark. ThiNet achieves 3.31× FLOPs reduction and 16.63× compression on VGG-16, with only 0.52% top-5 accuracy drop. Similar experiments with ResNet-50 reveal that even for a compact network, ThiNet can also reduce more than half of the parameters and FLOPs, at the cost of roughly 1% top-5 accuracy drop. Moreover, the original VGG-16 model can be further pruned into a very small model with only 5.05MB model size, preserving AlexNet level accuracy but showing much stronger generalization ability.

Low-rankness plays an important role in traditional machine learning, but is not so popular in deep learning. Most previous low-rank network compression methods compress the networks by approximating pre-trained models and re-training. However, the optimal solution in the Euclidean space may be quite different from the one in the low-rank manifold. A well-pre-trained model is not a good initialization for the model with low-rank constraints. Thus, the performance of a low-rank compressed network degrades significantly. Compared to other network compression methods such as pruning, low-rank methods attracts less attention in recent years. In this paper, we devise a new training method, low-rank projection with energy transfer (LRPET), that trains low-rank compressed networks from scratch and achieves competitive performance. First, we propose to alternately perform stochastic gradient descent training and projection onto the low-rank manifold. Compared to re-training on the compact model, this enables full utilization of model capacity since solution space is relaxed back to Euclidean space after projection. Second, the matrix energy (the sum of squares of singular values) reduction caused by projection is compensated by energy transfer. We uniformly transfer the energy of the pruned singular values to the remaining ones. We theoretically show that energy transfer eases the trend of gradient vanishing caused by projection. Third, we propose batch normalization (BN) rectification to cut off its effect on the optimal low-rank approximation of the weight matrix, which further improves the performance. Comprehensive experiments on CIFAR-10 and ImageNet have justified that our method is superior to other low-rank compression methods and also outperforms recent state-of-the-art pruning methods. Our code is available at https://github.com/BZQLin/LRPET.

过滤器修剪的目标是搜索不重要的过滤器以删除以便使卷积神经网络（CNNS）有效而不牺牲过程中的性能。挑战在于找到可以帮助确定每个过滤器关于神经网络的最终输出的重要或相关的信息的信息。在这项工作中，我们分享了我们的观察说，预先训练的CNN的批量标准化（BN）参数可用于估计激活输出的特征分布，而无需处理训练数据。在观察时，我们通过基于预先训练的CNN的BN参数评估每个滤波器的重要性来提出简单而有效的滤波修剪方法。 CiFar-10和Imagenet的实验结果表明，该方法可以在准确性下降和计算复杂性的计算复杂性和降低的折衷方面具有和不进行微调的卓越性能。

网络的稀疏性主要是由于其降低网络复杂性的能力而受欢迎。广泛的研究挖掘了梯度驱动的稀疏性。通常，这些方法是在体重独立性前提下构建的，但是与重量受到相互影响的事实相反。因此，他们的性能仍有待改进。在本文中，我们建议通过解决这种独立悖论来进一步优化梯度驱动的稀疏性（OPTG）。我们的动机来自最近对超级策略训练的进步，该进步表明，稀疏子网可以通过简单地更新掩码值而无需修改任何权重的情况下将其位于随机初始化的网络中。我们证明，超级手机训练是积累重量梯度，并可以部分解决独立悖论。因此，OPTG将Supermask训练集成到梯度驱动的稀疏度中，并且设计了专门的掩模优化器来解决独立悖论。实验表明，OPTG可以很好地超越许多现有的最先进的竞争对手。我们的代码可在\ url {https://github.com/zyxxmu/optg}上找到。

网络修剪是一种有效的方法，可以通过可接受的性能妥协降低网络复杂性。现有研究通过耗时的重量调谐或具有扩展宽度的网络的复杂搜索来实现神经网络的稀疏性，这极大地限制了网络修剪的应用。在本文中，我们表明，在没有权重调谐的情况下，高性能和稀疏的子网被称为“彩票奖线”，存在于具有膨胀宽度的预先训练的模型中。例如，我们获得了一个只有10％参数的彩票奖金，仍然达到了原始密度Vggnet-19的性能，而无需对CiFar-10的预先训练的重量进行任何修改。此外，我们观察到，来自许多现有修剪标准的稀疏面具与我们的彩票累积的搜索掩码具有高重叠，其中，基于幅度的修剪导致与我们的最相似的掩模。根据这种洞察力，我们使用基于幅度的修剪初始化我们的稀疏掩模，导致彩票累积搜索至少3倍降低，同时实现了可比或更好的性能。具体而言，我们的幅度基彩票奖学金在Reset-50中除去90％的重量，而在ImageNet上仅使用10个搜索时期可以轻松获得超过70％的前1个精度。我们的代码可在https://github.com/zyxxmu/lottery-jackpots获得。

虽然网络稀疏作为克服神经网络大小的有希望的方向，但它仍然是保持模型准确性的开放问题，并在一般CPU上实现了显着的加速。在本文中，我们提出了一篇新颖的1美元\ Times N $块稀疏模式（块修剪）的概念来打破这种限制。特别是，具有相同输入通道索引的连续$ N $输出内核被分组为一个块，该块用作我们修剪模式的基本修剪粒度。我们的$ 1 \ times n $ sparsity模式prunes这些块被认为不重要。我们还提供过滤器重新排列的工作流程，首先重新排列输出通道尺寸中的权重矩阵，以获得更具影响力的块，以便精度改进，然后将类似的重新排列到输入通道维度中的下一层权重，以确保正确的卷积操作。此外，可以通过并行化块 - 方向的矢量化操作实现在我们的$ 1 \ Times N $块稀疏之后的输出计算，从而导致总基于CPU的平台上的显着加速。通过对ILSVRC-2012的实验证明了我们修剪模式的功效。例如，在50％的稀疏性和$ n = 4 $的情况下，我们的模式在MobileNet-V2的前1个精度的过滤器修剪中获得了大约3.0％的改进。同时，它在Cortex-A7 CPU上获得56.04ms推断，超过体重修剪。代码可在https://github.com/lmbxmu/1xn处获得。

神经网络修剪具有显着性能，可以降低深网络模型的复杂性。最近的网络修剪方法通常集中在网络中删除不重要或冗余过滤器。在本文中，通过探索特征图之间的相似性，我们提出了一种新颖的滤波器修剪方法，中央滤波器（CF），这表明在适当的调整之后滤波器大致等于一组其他滤波器。我们的方法基于发现特征贴图之间的平均相似性的发现，而不管输入图像的数量如何，都会很少变化。基于此发现，我们在特征映射上建立相似性图，并计算每个节点的近密中心以选择中央滤波器。此外，我们设计一种方法，可以在与中央滤波器对应的下一层中直接调整权重，有效地最小化由修剪引起的误差。通过对各种基准网络和数据集的实验，CF产生最先进的性能。例如，对于Reset-56，CF通过去除47.1％的参数来减少约39.7％的絮凝物，甚至在CiFar-10上的精度改善0.33％。通过Googlenet，CF通过去除55.6％的参数来减少大约63.2％的拖鞋，仅在CIFAR-10上的前1个精度下降0.35％的损失。通过resnet-50，CF通过去除36.9％的参数减少约47.9％的拖鞋，仅在Imagenet上的前1个精度下降1.07％。该代码可以在https://github.com/8ubpshlr23/centrter上获得。

在过去几年中，神经网络的性能在越来越多的浮点操作（拖鞋）的成本上显着提高。但是，当计算资源有限时，更多的拖鞋可能是一个问题。作为解决这个问题的尝试，修剪过滤器是一种常见的解决方案，但大多数现有的修剪方法不有效地保持模型精度，因此需要大量的芬降时期。在本文中，我们提出了一种自动修剪方法，该方法学习保存的神经元以保持模型精度，同时将絮凝到预定目标。为了完成这项任务，我们介绍了一种可训练的瓶颈，只需要一个单一的单一时期，只需要一个数据集的25.6％（Cifar-10）或7.49％（ILSVRC2012）来了解哪些过滤器。在各种架构和数据集上的实验表明，该方法不仅可以在修剪后保持精度，而且在FineTuning之后也优越现有方法。我们在Reset-50上达到了52.00％的拖鞋，在ILSVRC2012上的灌溉后的前1个精度为47.51％，最先进的（SOTA）精度为76.63％。代码可用（链接匿名审核）。

通道修剪被广泛用于降低深网模型的复杂性。最近的修剪方法通常通过提出通道重要性标准来识别网络的哪些部分。但是，最近的研究表明，这些标准在所有情况下都不能很好地工作。在本文中，我们提出了一种新颖的功能最小化方法（FSM）方法来压缩CNN模型，该模型通过收敛功能和过滤器的信息来评估特征转移。具体而言，我们首先使用不同层深度的一些普遍方法研究压缩效率，然后提出特征转移概念。然后，我们引入了一种近似方法来估计特征移位的幅度，因为很难直接计算它。此外，我们提出了一种分布优化算法，以补偿准确性损失并提高网络压缩效率。该方法在各种基准网络和数据集上产生最先进的性能，并通过广泛的实验验证。这些代码可以在\ url {https://github.com/lscgx/fsm}上可用。

现有的可区分通道修剪方法通常将缩放因子或掩模在通道后面的掩盖范围内，以减少重要性的修剪过滤器，并假设输入样品统一贡献以过滤重要性。具体而言，实例复杂性对修剪性能的影响尚未得到充分研究。在本文中，我们提出了一个基于实例复杂性滤波器的重要性得分的简单而有效的可区分网络修剪方法上限。我们通过给硬样品给出更高的权重来定义每个样品的实例复杂性与重量相关的重量，并测量样品特异性软膜的加权总和，以模拟不同输入的非均匀贡献，这鼓励硬样品主导修剪过程和模型性能保存完好。此外，我们还引入了一个新的正规器，以鼓励面具两极分化，以便很容易找到甜蜜的位置以识别要修剪的过滤器。各种网络体系结构和数据集的性能评估表明，CAP在修剪大型网络方面具有优势。例如，CAP在删除65.64％的拖鞋后，CAP在CIFAR-10数据集上的RESNET56的准确性提高了0.33％，而Prunes在ImagEnet数据集上的RESNET50的PRUNES 87.75％，只有0.89％的TOP-1精度损失。

Structural pruning of neural network parameters reduces computation, energy, and memory transfer costs during inference. We propose a novel method that estimates the contribution of a neuron (filter) to the final loss and iteratively removes those with smaller scores. We describe two variations of our method using the first and secondorder Taylor expansions to approximate a filter's contribution. Both methods scale consistently across any network layer without requiring per-layer sensitivity analysis and can be applied to any kind of layer, including skip connections. For modern networks trained on ImageNet, we measured experimentally a high (>93%) correlation between the contribution computed by our methods and a reliable estimate of the true importance. Pruning with the proposed methods leads to an improvement over state-ofthe-art in terms of accuracy, FLOPs, and parameter reduction. On ResNet-101, we achieve a 40% FLOPS reduction by removing 30% of the parameters, with a loss of 0.02% in the top-1 accuracy on ImageNet. Code is available at https://github.com/NVlabs/Taylor_pruning.

The success of CNNs in various applications is accompanied by a significant increase in the computation and parameter storage costs. Recent efforts toward reducing these overheads involve pruning and compressing the weights of various layers without hurting original accuracy. However, magnitude-based pruning of weights reduces a significant number of parameters from the fully connected layers and may not adequately reduce the computation costs in the convolutional layers due to irregular sparsity in the pruned networks. We present an acceleration method for CNNs, where we prune filters from CNNs that are identified as having a small effect on the output accuracy. By removing whole filters in the network together with their connecting feature maps, the computation costs are reduced significantly. In contrast to pruning weights, this approach does not result in sparse connectivity patterns. Hence, it does not need the support of sparse convolution libraries and can work with existing efficient BLAS libraries for dense matrix multiplications. We show that even simple filter pruning techniques can reduce inference costs for VGG-16 by up to 34% and ResNet-110 by up to 38% on CIFAR10 while regaining close to the original accuracy by retraining the networks.

To reduce the significant redundancy in deep Convolutional Neural Networks (CNNs), most existing methods prune neurons by only considering statistics of an individual layer or two consecutive layers (e.g., prune one layer to minimize the reconstruction error of the next layer), ignoring the effect of error propagation in deep networks. In contrast, we argue that it is essential to prune neurons in the entire neuron network jointly based on a unified goal: minimizing the reconstruction error of important responses in the "final response layer" (FRL), which is the secondto-last layer before classification, for a pruned network to retrain its predictive power. Specifically, we apply feature ranking techniques to measure the importance of each neuron in the FRL, and formulate network pruning as a binary integer optimization problem and derive a closed-form solution to it for pruning neurons in earlier layers. Based on our theoretical analysis, we propose the Neuron Importance Score Propagation (NISP) algorithm to propagate the importance scores of final responses to every neuron in the network. The CNN is pruned by removing neurons with least importance, and then fine-tuned to retain its predictive power. NISP is evaluated on several datasets with multiple CNN models and demonstrated to achieve significant acceleration and compression with negligible accuracy loss.