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在pytorch中获取模型的可训练和不可训练的参数，层名称，内核大小和数量。
Pytorch nn.Module 类中没有提供像与Keras那样的可以计算模型中可训练和不可训练的参数的数量并显示模型摘要的方法 。所以在这篇文章中，我将总结我知道三种方法来计算Pytorch模型中可训练和不可训练的参数的数量。
直接手写代码
最直接的办法就是我们自己手写代码代码实现这个功能，所以这里我自己实现了一个函数，函数中为了漂亮所以引入了PrettyTable的包
代码语言：javascript复制 from prettytable import PrettyTable
def count_parameters(model):
table = PrettyTable([“Modules”, “Parameters”])
total_params = 0
for name, parameter in model.named_parameters():
if not parameter.requires_grad: continue
params = parameter.numel()
table.add_row([name, params])
total_params =params
print(table)
print(f”Total Trainable Params: {total_params}”)
return total_params我们拿RESNET18为例，以上函数的输出如下：
代码语言：javascript复制 ------------------------------ ------------
| Modules | Parameters |
------------------------------ ------------
| conv1.weight | 9408 |
| bn1.weight | 64 |
| bn1.bias | 64 |
| layer1.0.conv1.weight | 36864 |
| layer1.0.bn1.weight | 64 |
| layer1.0.bn1.bias | 64 |
.
.
.
| fc.weight | 512000 |
| fc.bias | 1000 |
------------------------------ ------------
Total Trainable Params: 11689512输出以参数为单位，可以看到模型中存在的每个参数的可训练参数，是不是和keras的基本一样。
torchsummary
torchsummary出现的时候的目标就是为了让torch有类似keras一样的打印模型参数的功能，它非常友好并且十分简单。当前版本为1.5.1，可以直接使用pip安装：
代码语言：javascript复制 pip install torchsummary安装完成后即可使用，我们还是以resnet18为例
代码语言：javascript复制 from torchsummary import summary
model = torchvision.models.resnet18().cuda()在使用时，我们需要生成一个模型的输入变量，也就是模拟模型的前向传播的过程：
代码语言：javascript复制 summary(model, input_size = (3, 64, 64), batch_size = -1)结果如下：
代码语言：javascript复制 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —
Layer (type) Output Shape Param # ================================================================
Conv2d-1 [-1, 64, 112, 112] 9,408
BatchNorm2d-2 [-1, 64, 112, 112] 128
ReLU-3 [-1, 64, 112, 112] 0
MaxPool2d-4 [-1, 64, 56, 56] 0
Conv2d-5 [-1, 64, 56, 56] 36,864
.
.
.
AdaptiveAvgPool2d-67 [-1, 512, 1, 1] 0
Linear-68 [-1, 1000] 513,000 ================================================================
Total params: 11,689,512
Trainable params: 11,689,512
Non-trainable params: 0
----------------------------------------------------------------
Input size (MB): 0.57
Forward/backward pass size (MB): 62.79
Params size (MB): 44.59
Estimated Total Size (MB): 107.96
----------------------------------------------------------------现在，如果你的基本模型有多个分支，每个分支都有不同的输入，例如
代码语言：javascript复制 class Model(torch.nn.Module):
def __init__(self):
super().__init__()
self.resnet1 = torchvision.models.resnet18().cuda()
self.resnet2 = torchvision.models.resnet18().cuda()
self.resnet3 = torchvision.models.resnet18().cuda()
def forward(self, *x):
out1 = self.resnet1(x[0])
out2 = self.resnet2(x[1])
out3 = self.resnet3(x[2])
out = torch.cat([out1, out2, out3], dim = 0)
return out那么就需要这样：
代码语言：javascript复制 summary(Model().cuda(), input_size = [(3, 64, 64)]*3)该输出将与前一个相似，但会有点混乱，因为torchsummary将每个组成的ResNet模块的信息压缩到一个摘要中，而在两个连续模块的摘要之间没有任何适当的可区分边界。
torchinfo
它看起来可能与torchsummary类似。但在我看来，它是我找到这三种方法中最好的。torchinfo当前版本是1.7.0，还是可以使用pip安装：
代码语言：javascript复制 pip install torchinfo这个包也有一个名为summary的函数。但它有更多的参数。他的使用参数为model (nn.module)、input_size (Sequence of Sizes)、input_data (Sequence of Tensors)、batch_dim (int)、cache_forward_pass (bool)、col_names (Iterable[str])、col_width (int)、depth (int)、device (torch.Device)、dtypes (List[torch.dtype])、mode (str)、row_settings (Iterable[str])、verbose (int)和**kwargs。
参数很多，但是可以直接通过(" input_size "， " output_size "， " num_params "， " kernel_size "， " mult_add "， " trainable ")作为col_names参数来获取信息。
代码语言：javascript复制 import torchinfo
torchinfo.summary(model, (3, 224, 224), batch_dim = 0, col_names = (“input_size”, “output_size”, “num_params”, “kernel_size”, “mult_adds”), verbose = 0)需要说明的是，如果不使用Jupyter或Google Colab，需要将verbose 更改为1。
上述代码段的输出看起来像这样
代码语言：javascript复制 =============================================================================================
Layer (type:depth-idx) Input Shape Output Shape Param # Kernel Shape Mult-Adds
=============================================================================================
ResNet [1, 3, 224, 224] [1, 1000] -- -- --
├─Conv2d: 1-1 [1, 3, 224, 224] [1, 64, 112, 112] 9,408 [7, 7] 118,013,952
├─BatchNorm2d: 1-2 [1, 64, 112, 112] [1, 64, 112, 112] 128 -- 128
├─ReLU: 1-3 [1, 64, 112, 112] [1, 64, 112, 112] -- -- --
├─MaxPool2d: 1-4 [1, 64, 112, 112] [1, 64, 56, 56] -- 3 --
├─Sequential: 1-5 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
│ └─BasicBlock: 2-1 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
│ │ └─Conv2d: 3-1 [1, 64, 56, 56] [1, 64, 56, 56] 36,864 [3, 3] 115,605,504
│ │ └─BatchNorm2d: 3-2 [1, 64, 56, 56] [1, 64, 56, 56] 128 -- 128
│ │ └─ReLU: 3-3 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
│ │ └─Conv2d: 3-4 [1, 64, 56, 56] [1, 64, 56, 56] 36,864 [3, 3] 115,605,504
│ │ └─BatchNorm2d: 3-5 [1, 64, 56, 56] [1, 64, 56, 56] 128 -- 128
│ │ └─ReLU: 3-6 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
│ └─BasicBlock: 2-2 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
│ │ └─Conv2d: 3-7 [1, 64, 56, 56] [1, 64, 56, 56] 36,864 [3, 3] 115,605,504
│ │ └─BatchNorm2d: 3-8 [1, 64, 56, 56] [1, 64, 56, 56] 128 -- 128
│ │ └─ReLU: 3-9 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
│ │ └─Conv2d: 3-10 [1, 64, 56, 56] [1, 64, 56, 56] 36,864 [3, 3] 115,605,504
│ │ └─BatchNorm2d: 3-11 [1, 64, 56, 56] [1, 64, 56, 56] 128 -- 128
│ │ └─ReLU: 3-12 [1, 64, 56, 56] [1, 64, 56, 56] -- -- --
├─Sequential: 1-6 [1, 64, 56, 56] [1, 128, 28, 28] -- -- --
│ └─BasicBlock: 2-3 [1, 64, 56, 56] [1, 128, 28, 28] -- -- --
│ │ └─Conv2d: 3-13 [1, 64, 56, 56] [1, 128, 28, 28] 73,728 [3, 3] 57,802,752
│ │ └─BatchNorm2d: 3-14 [1, 128, 28, 28] [1, 128, 28, 28] 256 -- 256
.
.
.
│ │ └─Conv2d: 3-49 [1, 512, 7, 7] [1, 512, 7, 7] 2,359,296 [3, 3] 115,605,504
│ │ └─BatchNorm2d: 3-50 [1, 512, 7, 7] [1, 512, 7, 7] 1,024 -- 1,024
│ │ └─ReLU: 3-51 [1, 512, 7, 7] [1, 512, 7, 7] -- -- --
├─AdaptiveAvgPool2d: 1-9 [1, 512, 7, 7] [1, 512, 1, 1] -- -- --
├─Linear: 1-10 [1, 512] [1, 1000] 513,000 -- 513,000
=============================================================================================
Total params: 11,689,512
Trainable params: 11,689,512
Non-trainable params: 0
Total mult-adds (G): 1.81
=============================================================================================
Input size (MB): 0.60
Forward/backward pass size (MB): 39.75
Params size (MB): 46.76
Estimated Total Size (MB): 87.11
=============================================================================================再继续查看多分支模型
代码语言：javascript复制 torchinfo.summary(Model().cuda(), [(3, 64, 64)]*3, batch_dim = 0, col_names = (“input_size”, “output_size”, “num_params”, “kernel_size”, “mult_adds”), verbose = 0)产生以下输出
代码语言：javascript复制 =============================================================================================
Layer (type:depth-idx) Input Shape Output Shape Param # Kernel Shape Mult-Adds
=============================================================================================
Model [1, 3, 64, 64] [1, 1000] -- -- --
├─ResNet: 1-1 [1, 3, 64, 64] [1, 1000] -- -- --
│ └─Conv2d: 2-1 [1, 3, 64, 64] [1, 64, 32, 32] 9,408 [7, 7] 9,633,792
│ └─BatchNorm2d: 2-2 [1, 64, 32, 32] [1, 64, 32, 32] 128 -- 128
│ └─ReLU: 2-3 [1, 64, 32, 32] [1, 64, 32, 32] -- -- --
│ └─MaxPool2d: 2-4 [1, 64, 32, 32] [1, 64, 16, 16] -- 3 --
│ └─Sequential: 2-5 [1, 64, 16, 16] [1, 64, 16, 16] -- -- --
│ │ └─BasicBlock: 3-1 [1, 64, 16, 16] [1, 64, 16, 16] 73,984 -- 18,874,624
│ │ └─BasicBlock: 3-2 [1, 64, 16, 16] [1, 64, 16, 16] 73,984 -- 18,874,624
│ └─Sequential: 2-6 [1, 64, 16, 16] [1, 128, 8, 8] -- -- --
│ │ └─BasicBlock: 3-3 [1, 64, 16, 16] [1, 128, 8, 8] 230,144 -- 14,680,832
│ │ └─BasicBlock: 3-4 [1, 128, 8, 8] [1, 128, 8, 8] 295,424 -- 18,874,880
│ └─Sequential: 2-7 [1, 128, 8, 8] [1, 256, 4, 4] -- -- --
│ │ └─BasicBlock: 3-5 [1, 128, 8, 8] [1, 256, 4, 4] 919,040 -- 14,681,600
│ │ └─BasicBlock: 3-6 [1, 256, 4, 4] [1, 256, 4, 4] 1,180,672 -- 18,875,392
│ └─Sequential: 2-8 [1, 256, 4, 4] [1, 512, 2, 2] -- -- --
│ │ └─BasicBlock: 3-7 [1, 256, 4, 4] [1, 512, 2, 2] 3,673,088 -- 14,683,136
│ │ └─BasicBlock: 3-8 [1, 512, 2, 2] [1, 512, 2, 2] 4,720,640 -- 18,876,416
│ └─AdaptiveAvgPool2d: 2-9 [1, 512, 2, 2] [1, 512, 1, 1] -- -- --
│ └─Linear: 2-10 [1, 512] [1, 1000] 513,000 -- 513,000
├─ResNet: 1-2 [1, 3, 64, 64] [1, 1000] -- -- --
│ └─Conv2d: 2-11 [1, 3, 64, 64] [1, 64, 32, 32] 9,408 [7, 7] 9,633,792
│ └─BatchNorm2d: 2-12 [1, 64, 32, 32] [1, 64, 32, 32] 128 -- 128
│ └─ReLU: 2-13 [1, 64, 32, 32] [1, 64, 32, 32] -- -- --
│ └─MaxPool2d: 2-14 [1, 64, 32, 32] [1, 64, 16, 16] -- 3 --
│ └─Sequential: 2-15 [1, 64, 16, 16] [1, 64, 16, 16] -- -- --
│ │ └─BasicBlock: 3-9 [1, 64, 16, 16] [1, 64, 16, 16] 73,984 -- 18,874,624
│ │ └─BasicBlock: 3-10 [1, 64, 16, 16] [1, 64, 16, 16] 73,984 -- 18,874,624
│ └─Sequential: 2-16 [1, 64, 16, 16] [1, 128, 8, 8] -- -- --
│ │ └─BasicBlock: 3-11 [1, 64, 16, 16] [1, 128, 8, 8] 230,144 -- 14,680,832
│ │ └─BasicBlock: 3-12 [1, 128, 8, 8] [1, 128, 8, 8] 295,424 -- 18,874,880
│ └─Sequential: 2-17 [1, 128, 8, 8] [1, 256, 4, 4] -- -- --
│ │ └─BasicBlock: 3-13 [1, 128, 8, 8] [1, 256, 4, 4] 919,040 -- 14,681,600
│ │ └─BasicBlock: 3-14 [1, 256, 4, 4] [1, 256, 4, 4] 1,180,672 -- 18,875,392
│ └─Sequential: 2-18 [1, 256, 4, 4] [1, 512, 2, 2] -- -- --
│ │ └─BasicBlock: 3-15 [1, 256, 4, 4] [1, 512, 2, 2] 3,673,088 -- 14,683,136
│ │ └─BasicBlock: 3-16 [1, 512, 2, 2] [1, 512, 2, 2] 4,720,640 -- 18,876,416
│ └─AdaptiveAvgPool2d: 2-19 [1, 512, 2, 2] [1, 512, 1, 1] -- -- --
│ └─Linear: 2-20 [1, 512] [1, 1000] 513,000 -- 513,000
├─ResNet: 1-3 [1, 3, 64, 64] [1, 1000] -- -- --
│ └─Conv2d: 2-21 [1, 3, 64, 64] [1, 64, 32, 32] 9,408 [7, 7] 9,633,792
│ └─BatchNorm2d: 2-22 [1, 64, 32, 32] [1, 64, 32, 32] 128 -- 128
│ └─ReLU: 2-23 [1, 64, 32, 32] [1, 64, 32, 32] -- -- --
│ └─MaxPool2d: 2-24 [1, 64, 32, 32] [1, 64, 16, 16] -- 3 --
│ └─Sequential: 2-25 [1, 64, 16, 16] [1, 64, 16, 16] -- -- --
│ │ └─BasicBlock: 3-17 [1, 64, 16, 16] [1, 64, 16, 16] 73,984 -- 18,874,624
│ │ └─BasicBlock: 3-18 [1, 64, 16, 16] [1, 64, 16, 16] 73,984 -- 18,874,624
│ └─Sequential: 2-26 [1, 64, 16, 16] [1, 128, 8, 8] -- -- --
│ │ └─BasicBlock: 3-19 [1, 64, 16, 16] [1, 128, 8, 8] 230,144 -- 14,680,832
│ │ └─BasicBlock: 3-20 [1, 128, 8, 8] [1, 128, 8, 8] 295,424 -- 18,874,880
│ └─Sequential: 2-27 [1, 128, 8, 8] [1, 256, 4, 4] -- -- --
│ │ └─BasicBlock: 3-21 [1, 128, 8, 8] [1, 256, 4, 4] 919,040 -- 14,681,600
│ │ └─BasicBlock: 3-22 [1, 256, 4, 4] [1, 256, 4, 4] 1,180,672 -- 18,875,392
│ └─Sequential: 2-28 [1, 256, 4, 4] [1, 512, 2, 2] -- -- --
│ │ └─BasicBlock: 3-23 [1, 256, 4, 4] [1, 512, 2, 2] 3,673,088 -- 14,683,136
│ │ └─BasicBlock: 3-24 [1, 512, 2, 2] [1, 512, 2, 2] 4,720,640 -- 18,876,416
│ └─AdaptiveAvgPool2d: 2-29 [1, 512, 2, 2] [1, 512, 1, 1] -- -- --
│ └─Linear: 2-30 [1, 512] [1, 1000] 513,000 -- 513,000
=============================================================================================
Total params: 35,068,536
Trainable params: 35,068,536
Non-trainable params: 0
Total mult-adds (M): 445.71
=============================================================================================
Input size (MB): 0.15
Forward/backward pass size (MB): 9.76
Params size (MB): 140.27
Estimated Total Size (MB): 150.18
=============================================================================================可以看到depth 参数的默认值为3。并且在可视化方向上，多分支被重新进行了组织并且以层次结构方式呈现，所以很容易区分，所以他的效果要比torchsummary好很多。
作者：Siladittya Manna
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