from torch.autograd import Variable

时间: 2023-09-23 19:13:24 浏览: 20
As an AI language model, I am not able to execute code. However, I can provide you with information about the `torch.autograd.Variable` function in PyTorch. `torch.autograd.Variable` is a class that holds a tensor and its gradient. It is a fundamental building block for performing automatic differentiation in PyTorch. When a tensor is wrapped in a `Variable`, PyTorch keeps track of all the operations performed on it, allowing you to calculate gradients automatically using the chain rule. For example, if you have a tensor `x` and you want to compute its gradient with respect to some other tensor `y`, you can create a `Variable` object for `x` and use it to compute the gradient: ``` import torch x = torch.tensor([1.0, 2.0, 3.0], requires_grad=True) y = 2 * x + 1 z = y.mean() z.backward() ``` In this example, `x` is a tensor that requires a gradient (i.e., we want to compute the derivative of `z` with respect to `x`). We create a `Variable` object for `x` by setting the `requires_grad` flag to `True`. We then perform some operations on `x` to compute `y` and `z`. Finally, we call `backward()` on `z` to compute the gradients, which are stored in the `grad` attribute of `x`. Note that in recent versions of PyTorch, the `Variable` class has been deprecated in favor of directly using tensors with the `requires_grad` flag. The above example can be rewritten as: ``` import torch x = torch.tensor([1.0, 2.0, 3.0], requires_grad=True) y = 2 * x + 1 z = y.mean() z.backward() ```

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#encoding=utf8 import torch import torch.nn as nn from torch.autograd import Variable import torch.utils.data as Data import torchvision import os class CNN(nn.Module): def __init__(self): super(CNN, self).__init__() self.conv1 = nn.Sequential( nn.Conv2d( in_channels=1, out_channels=16, kernel_size=5, stride=1, padding=2, ), nn.ReLU(), nn.MaxPool2d(kernel_size=2), ) self.conv2 = nn.Sequential( nn.Conv2d(16, 32, 5, 1, 2), nn.ReLU(), nn.MaxPool2d(2), ) self.out = nn.Linear(32 * 7 * 7, 10) def forward(self, x): x = self.conv1(x) x = self.conv2(x) x = x.view(x.size(0), -1) output = self.out(x) return output #加载数据 train_data = torchvision.datasets.MNIST( root='/data/workspace/course/step3/mnist', train=True, transform=torchvision.transforms.ToTensor(), download=False, ) #取6000个样本为训练集 train_data_tiny = [] for i in range(6000): train_data_tiny.append(train_data[i]) train_data = train_data_tiny #实例化CNN模型 cnn = CNN() #定义损失函数 loss_func = nn.CrossEntropyLoss() #定义优化器 optimizer = torch.optim.Adam(cnn.parameters(), lr=0.01) #定义数据加载器 train_loader = Data.DataLoader(dataset=train_data, batch_size=64, shuffle=True) #开始训练 for epoch in range(10): for step, (x, y) in enumerate(train_loader): b_x = Variable(x) b_y = Variable(y) output = cnn(b_x) loss = loss_func(output, b_y) optimizer.zero_grad() loss.backward() optimizer.step() if step % 50 == 0: test_output = cnn(torch.unsqueeze(train_data_tiny[0][0], dim=0)) pred_y = torch.max(test_output, 1)[1].data.numpy().squeeze() accuracy = sum(pred_y == train_data_tiny[0][1]) / float(train_data_tiny[0][1].shape[0]) print('Epoch: ', epoch, '| train loss: %.4f' % loss.data.numpy(), '| test accuracy: %.2f' % accuracy) #保存模型 torch.save(cnn.state_dict(), '/data/workspace/course/step3/cnn.pkl')

运行以下Python代码:import torchimport torch.nn as nnimport torch.optim as optimfrom torchvision import datasets, transformsfrom torch.utils.data import DataLoaderfrom torch.autograd import Variableclass Generator(nn.Module): def __init__(self, input_dim, output_dim, num_filters): super(Generator, self).__init__() self.input_dim = input_dim self.output_dim = output_dim self.num_filters = num_filters self.net = nn.Sequential( nn.Linear(input_dim, num_filters), nn.ReLU(), nn.Linear(num_filters, num_filters*2), nn.ReLU(), nn.Linear(num_filters*2, num_filters*4), nn.ReLU(), nn.Linear(num_filters*4, output_dim), nn.Tanh() ) def forward(self, x): x = self.net(x) return xclass Discriminator(nn.Module): def __init__(self, input_dim, num_filters): super(Discriminator, self).__init__() self.input_dim = input_dim self.num_filters = num_filters self.net = nn.Sequential( nn.Linear(input_dim, num_filters*4), nn.LeakyReLU(0.2), nn.Linear(num_filters*4, num_filters*2), nn.LeakyReLU(0.2), nn.Linear(num_filters*2, num_filters), nn.LeakyReLU(0.2), nn.Linear(num_filters, 1), nn.Sigmoid() ) def forward(self, x): x = self.net(x) return xclass ConditionalGAN(object): def __init__(self, input_dim, output_dim, num_filters, learning_rate): self.generator = Generator(input_dim, output_dim, num_filters) self.discriminator = Discriminator(input_dim+1, num_filters) self.optimizer_G = optim.Adam(self.generator.parameters(), lr=learning_rate) self.optimizer_D = optim.Adam(self.discriminator.parameters(), lr=learning_rate) def train(self, data_loader, num_epochs): for epoch in range(num_epochs): for i, (inputs, labels) in enumerate(data_loader): # Train discriminator with real data real_inputs = Variable(inputs) real_labels = Variable(labels) real_labels = real_labels.view(real_labels.size(0), 1) real_inputs = torch.cat((real_inputs, real_labels), 1) real_outputs = self.discriminator(real_inputs) real_loss = nn.BCELoss()(real_outputs, torch.ones(real_outputs.size())) # Train discriminator with fake data noise = Variable(torch.randn(inputs.size(0), self.generator.input_dim)) fake_labels = Variable(torch.LongTensor(inputs.size(0)).random_(0, 10)) fake_labels = fake_labels.view(fake_labels.size(0), 1) fake_inputs = self.generator(torch.cat((noise, fake_labels.float()), 1)) fake_inputs = torch.cat((fake_inputs, fake_labels), 1) fake_outputs = self.discriminator(fake_inputs) fake_loss = nn.BCELoss()(fake_outputs, torch.zeros(fake_outputs.size())) # Backpropagate and update weights for discriminator discriminator_loss = real_loss + fake_loss self.discriminator.zero_grad() discriminator_loss.backward() self.optimizer_D.step() # Train generator noise = Variable(torch.randn(inputs.size(0), self.generator.input_dim)) fake_labels = Variable(torch.LongTensor(inputs.size(0)).random_(0,

这是一个用 PyTorch 实现的条件 GAN,以下是代码的简要解释: 首先引入 PyTorch 相关的库和模块: import torch import torch.nn as nn import torch.optim as optim from torchvision import datasets, transforms from torch.utils.data import DataLoader from torch.autograd import Variable 接下来定义生成器(Generator)和判别器(Discriminator)的类: class Generator(nn.Module): def __init__(self, input_dim, output_dim, num_filters): super(Generator, self).__init__() self.input_dim = input_dim self.output_dim = output_dim self.num_filters = num_filters self.net = nn.Sequential( nn.Linear(input_dim, num_filters), nn.ReLU(), nn.Linear(num_filters, num_filters*2), nn.ReLU(), nn.Linear(num_filters*2, num_filters*4), nn.ReLU(), nn.Linear(num_filters*4, output_dim), nn.Tanh() ) def forward(self, x): x = self.net(x) return x class Discriminator(nn.Module): def __init__(self, input_dim, num_filters): super(Discriminator, self).__init__() self.input_dim = input_dim self.num_filters = num_filters self.net = nn.Sequential( nn.Linear(input_dim, num_filters*4), nn.LeakyReLU(0.2), nn.Linear(num_filters*4, num_filters*2), nn.LeakyReLU(0.2), nn.Linear(num_filters*2, num_filters), nn.LeakyReLU(0.2), nn.Linear(num_filters, 1), nn.Sigmoid() ) def forward(self, x): x = self.net(x) return x 其中,生成器接受输入维度 input_dim、输出维度 output_dim 和 num_filters 个特征,采用线性层和激活函数构建多层神经网络。判别器接受输入维度 input_dim 和 num_filters 个特征,同样采用线性层和激活函数构建多层神经网络。 最后定义条件 GAN 的类 ConditionalGAN,该类包括生成器、判别器和优化器,以及 train 方法进行训练: class ConditionalGAN(object): def __init__(self, input_dim, output_dim, num_filters, learning_rate): self.generator = Generator(input_dim, output_dim, num_filters) self.discriminator = Discriminator(input_dim+1, num_filters) self.optimizer_G = optim.Adam(self.generator.parameters(), lr=learning_rate) self.optimizer_D = optim.Adam(self.discriminator.parameters(), lr=learning_rate) def train(self, data_loader, num_epochs): for epoch in range(num_epochs): for i, (inputs, labels) in enumerate(data_loader): ... 其中,ConditionalGAN 类接受输入维度 input_dim、输出维度 output_dim、特征数 num_filters 和学习率 learning_rate。train 方法则接受数据加载器 data_loader 和训练轮数 num_epochs,用于训练模型。

import torch import torch.nn as nn import torch.nn.functional as F from torch.autograd import Variable class Bottleneck(nn.Module): def init(self, last_planes, in_planes, out_planes, dense_depth, stride, first_layer): super(Bottleneck, self).init() self.out_planes = out_planes self.dense_depth = dense_depth self.conv1 = nn.Conv2d(last_planes, in_planes, kernel_size=1, bias=False) self.bn1 = nn.BatchNorm2d(in_planes) self.conv2 = nn.Conv2d(in_planes, in_planes, kernel_size=3, stride=stride, padding=1, groups=32, bias=False) self.bn2 = nn.BatchNorm2d(in_planes) self.conv3 = nn.Conv2d(in_planes, out_planes+dense_depth, kernel_size=1, bias=False) self.bn3 = nn.BatchNorm2d(out_planes+dense_depth) self.shortcut = nn.Sequential() if first_layer: self.shortcut = nn.Sequential( nn.Conv2d(last_planes, out_planes+dense_depth, kernel_size=1, stride=stride, bias=False), nn.BatchNorm2d(out_planes+dense_depth) ) def forward(self, x): out = F.relu(self.bn1(self.conv1(x))) out = F.relu(self.bn2(self.conv2(out))) out = self.bn3(self.conv3(out)) x = self.shortcut(x) d = self.out_planes out = torch.cat([x[:,:d,:,:]+out[:,:d,:,:], x[:,d:,:,:], out[:,d:,:,:]], 1) out = F.relu(out) return out class DPN(nn.Module): def init(self, cfg): super(DPN, self).init() in_planes, out_planes = cfg['in_planes'], cfg['out_planes'] num_blocks, dense_depth = cfg['num_blocks'], cfg['dense_depth'] self.conv1 = nn.Conv2d(3, 64, kernel_size=3, stride=1, padding=1, bias=False) self.bn1 = nn.BatchNorm2d(64) self.last_planes = 64 self.layer1 = self._make_layer(in_planes[0], out_planes[0], num_blocks[0], dense_depth[0], stride=1) self.layer2 = self._make_layer(in_planes[1], out_planes[1], num_blocks[1], dense_depth[1], stride=2) self.layer3 = self._make_layer(in_planes[2], out_planes[2], num_blocks[2], dense_depth[2], stride=2) self.layer4 = self._make_layer(in_planes[3], out_planes[3], num_blocks[3], dense_depth[3], stride=2) self.linear = nn.Linear(out_planes[3]+(num_blocks[3]+1)dense_depth[3], 10) def _make_layer(self, in_planes, out_planes, num_blocks, dense_depth, stride): strides = [stride] + 1 layers = [] for i,stride in (strides): layers.append(Bottleneck(self.last_planes, in_planes, out_planes, dense_depth, stride, i==0)) self.last_planes = out_planes + (i+2) * dense_depth return nn.Sequential(*layers) def forward(self, x): out = F.relu(self.bn1(self.conv1(x))) out = self.layer1(out) out = self.layer2(out) out = self.layer3(out) out = self.layer4(out) out = F.avg_pool2d(out, 4) out = out.view(out.size(0), -1) out = self.linear(out) return out def DPN92(): cfg = { 'in_planes': (96,192,384,768), 'out_planes': (256,512,1024,2048), 'num_blocks': (3,4,20,3), 'dense_depth': (16,32,24,128) } return DPN(cfg)基于这个程序改成对摄像头采集的图像检测与分类输出坐标、大小和种类

这个程序是一个深度残差网络(DPN)用于图像分类,需要进行较大的修改才能用于目标检测和分类。需要添加目标检测和分类的头部网络,以输出目标的坐标、大小和种类。同时需要将输入改为摄像头采集的图像。 以下是基于这个程序的修改建议: python import torch import torch.nn as nn import torch.nn.functional as F from torch.autograd import Variable class Bottleneck(nn.Module): def __init__(self, last_planes, in_planes, out_planes, dense_depth, stride, first_layer): super(Bottleneck, self).__init__() self.out_planes = out_planes self.dense_depth = dense_depth self.conv1 = nn.Conv2d(last_planes, in_planes, kernel_size=1, bias=False) self.bn1 = nn.BatchNorm2d(in_planes) self.conv2 = nn.Conv2d(in_planes, in_planes, kernel_size=3, stride=stride, padding=1, groups=32, bias=False) self.bn2 = nn.BatchNorm2d(in_planes) self.conv3 = nn.Conv2d(in_planes, out_planes * dense_depth, kernel_size=1, bias=False) self.bn3 = nn.BatchNorm2d(out_planes * dense_depth) self.shortcut = nn.Sequential() if first_layer: self.shortcut = nn.Sequential( nn.Conv2d(last_planes, out_planes * dense_depth, kernel_size=1, stride=stride, bias=False), nn.BatchNorm2d(out_planes * dense_depth) ) def forward(self, x): out = F.relu(self.bn1(self.conv1(x))) out = F.relu(self.bn2(self.conv2(out))) out = self.bn3(self.conv3(out)) x = self.shortcut(x) d = self.out_planes out = torch.cat([x[:, :d, :, :], out[:, :d, :, :], x[:, d:, :, :], out[:, d:, :, :]], 1) out = F.relu(out) return out class DPN(nn.Module): def __init__(self, cfg, num_classes): super(DPN, self).__init__() in_planes, out_planes = cfg['in_planes'], cfg['out_planes'] num_blocks, dense_depth = cfg['num_blocks'], cfg['dense_depth'] self.conv1 = nn.Conv2d(3, 64, kernel_size=3, stride=1, padding=1, bias=False) self.bn1 = nn.BatchNorm2d(64) self.last_planes = 64 self.layer1 = self._make_layer(in_planes[0], out_planes[0], num_blocks[0], dense_depth[0], stride=1) self.layer2 = self._make_layer(in_planes[1], out_planes[1], num_blocks[1], dense_depth[1], stride=2) self.layer3 = self._make_layer(in_planes[2], out_planes[2], num_blocks[2], dense_depth[2], stride=2) self.layer4 = self._make_layer(in_planes[3], out_planes[3], num_blocks[3], dense_depth[3], stride=2) self.avgpool = nn.AdaptiveAvgPool2d((1, 1)) self.fc = nn.Linear(out_planes[3] * dense_depth[3], num_classes * 5) # 输出目标的坐标、大小和种类 def _make_layer(self, in_planes, out_planes, num_blocks, dense_depth, stride): strides = [stride] + [1] * (num_blocks - 1) layers = [] for i, stride in enumerate(strides): layers.append(Bottleneck(self.last_planes, in_planes, out_planes, dense_depth, stride, i==0)) self.last_planes = out_planes * dense_depth return nn.Sequential(*layers) def forward(self, x): out = F.relu(self.bn1(self.conv1(x))) out = self.layer1(out) out = self.layer2(out) out = self.layer3(out) out = self.layer4(out) out = self.avgpool(out) out = out.view(out.size(0), -1) out = self.fc(out) return out def DPN92(num_classes=80): cfg = { 'in_planes': (96, 192, 384, 768), 'out_planes': (256, 512, 1024, 2048), 'num_blocks': (3, 4, 20, 3), 'dense_depth': (16, 32, 24, 128) } return DPN(cfg, num_classes) 在上述修改中,我们添加了一个新的类别数参数 num_classes,用于控制输出的目标种类数。同时将最后的全连接层 linear 替换为了一个新的全连接层 fc,输出目标的坐标、大小和种类。在 forward 函数中,我们添加了一个自适应平均池化层 avgpool,用于将最后一层特征图的大小缩小为 1x1。最后将特征图展平后送入全连接层 fc 进行分类和回归。

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