在PyTorch中，有几种不同的工具可以用于网络结构的可视化。下面将以ResNet-18为例，展示如何使用常用的PyTorch画图工具进行网络结构的可视化。
ResNet-18是一个经典的卷积神经网络模型，由多个卷积层、池化层、全连接层和残差连接（Residual Connection）组成。参考Deep Residual Learning for Image Recognition，网络结构如下：
在PyTorch中可以能过torchvision快速使用ResNet-18，使用代码如下：
from torchvision.models import resnet18
x = torch.randn(1, 3, 224, 224)
model = resnet18()x是随机生成的输入数据，model是resnet18的实例。
1. torch print
使用torch自带的print方法。torch的model支持直接print打印，可以看到详细的网络结构。
使用示例：
print(model)结果如下：
ResNet(
(conv1): Conv2d(3, 64, kernel_size=(7, 7), stride=(2, 2), padding=(3, 3), bias=False)
(bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(relu): ReLU(inplace=True)
(maxpool): MaxPool2d(kernel_size=3, stride=2, padding=1, dilation=1, ceil_mode=False)
(layer1): Sequential(
(0): BasicBlock(
(conv1): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1), bias=False)
(bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(relu): ReLU(inplace=True)
(conv2): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1), bias=False)
(bn2): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
)
(1): BasicBlock(
(conv1): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1), bias=False)
(bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(relu): ReLU(inplace=True)
(conv2): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1), bias=False)
(bn2): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
)
)
......2. torchsummary
代码库：https://github.com/sksq96/pytorch-summary
使用torchsummary进行model的打印，展示的信息比print会多出来参数量和shape信息
安装：
pip install torchsummary使用示例：
from torchsummary import summary
summary(model, x.squeeze(dim=0).shape)结果如下：
----------------------------------------------------------------
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
BatchNorm2d-6 [-1, 64, 56, 56] 128
ReLU-7 [-1, 64, 56, 56] 0
Conv2d-8 [-1, 64, 56, 56] 36,864
BatchNorm2d-9 [-1, 64, 56, 56] 128
ReLU-10 [-1, 64, 56, 56] 0
BasicBlock-11 [-1, 64, 56, 56] 0
Conv2d-12 [-1, 64, 56, 56] 36,864
BatchNorm2d-13 [-1, 64, 56, 56] 128
ReLU-14 [-1, 64, 56, 56] 0
Conv2d-15 [-1, 64, 56, 56] 36,864
BatchNorm2d-16 [-1, 64, 56, 56] 128
ReLU-17 [-1, 64, 56, 56] 0
BasicBlock-18 [-1, 64, 56, 56] 0
Conv2d-19 [-1, 128, 28, 28] 73,728
BatchNorm2d-20 [-1, 128, 28, 28] 256
ReLU-21 [-1, 128, 28, 28] 0
Conv2d-22 [-1, 128, 28, 28] 147,4563. torchviz
代码库：https://github.com/szagoruyko/pytorchviz
使用torchviz进行可视化（需要安装torchviz和graphviz）。torchviz会通过backward的过程对整个网络进行展示。
安装：
apt install python3-pydot python3-pydot-ng graphviz xdg-utils
pip install torchviz使用示例, 保存图片到文件中，如果终端直接展示的话render函数中的view配置改为True：
from torchviz import make_dot
y = model(x)
output = make_dot(y.mean(), params=dict(model.named_parameters()), show_attrs=True, show_saved=True)
output.format = "png"
output.directory = "."
output.render("torchviz", view=False)结果如下：
4. hiddenlayer
代码库：https://github.com/waleedka/hiddenlayer
hiddenlayer跟之前比的一个特色在于，hiddenlayer中支持transforms配置，可以对指定的多个连续算子进行fusion展示，以及有多个重复的结构的话可以进行fold压缩展示。
安装：
pip install matplotlib
pip install hiddenlayer使用示例：
import hiddenlayer as hl
transforms = [
# Fold repeated blocks
hl.transforms.FoldDuplicates(),
]
graph = hl.build_graph(model, x, transforms=transforms)
graph.theme = hl.graph.THEMES['blue'].copy()
graph.save('hiddenlayer', format='png')结果如下：
5. torchview
代码库：https://github.com/mert-kurttutan/torchview
安装：
pip install torchview使用示例：
from torchview import draw_graph
model_graph = draw_graph(model, input_size=x.shape, expand_nested=True, save_graph=True, filename="torchview", directory=".")
model_graph.visual_graph结果如下：
6. netron
代码库：https://github.com/lutzroeder/netron
netron可以对保存的模型文件进行可视化展示。介绍中支持的格式有：
Netron supports ONNX, TensorFlow Lite, Caffe, Keras, Darknet, PaddlePaddle, ncnn, MNN, Core ML, RKNN, MXNet, MindSpore Lite, TNN, Barracuda, Tengine, CNTK, TensorFlow.js, Caffe2 and UFF.
安装：
pip install onnx
pip install netron使用示例：
onnx_file_path = "resnet18.onnx"
torch.onnx.export(model, x, onnx_file_path, verbose=True)使用netron导入resnet18.onnx文件，结果如下：
7. 完整代码
#!/usr/bin/env python
import torch
import torch.nn as nn
from torchvision.models import resnet18
def draw_torchsummary(model, x):
from torchsummary import summary
summary(model, x.squeeze(dim=0).shape)
def draw_torchviz(model, x):
from torchviz import make_dot
y = model(x)
output = make_dot(y.mean(), params=dict(model.named_parameters()), show_attrs=True, show_saved=True)
output.format = "png"
output.directory = "."
output.render("torchviz", view=False)
def draw_torchview(model, x):
from torchview import draw_graph
model_graph = draw_graph(model, input_size=x.shape, expand_nested=True, save_graph=True, filename="torchview", directory=".")
#model_graph.visual_graph
def draw_hiddenlayer(model, x):
import hiddenlayer as hl
transforms = [
# Fold repeated blocks
hl.transforms.FoldDuplicates(),
]
graph = hl.build_graph(model, x, transforms=transforms)
graph.theme = hl.graph.THEMES['blue'].copy()
graph.save('hiddenlayer', format='png')
def draw_netron(model, x):
onnx_file_path = "resnet18.onnx"
torch.onnx.export(model, x, onnx_file_path, verbose=True)
if __name__ == "__main__":
x = torch.randn(1, 3, 224, 224)
model = resnet18()
print(model)
draw_torchsummary(model, x)
draw_torchviz(model, x)
draw_hiddenlayer(model, x)
draw_torchview(model, x)
draw_netron(model, x)
