Help!!! Does anyone knows how to insert a new layer in the middel of a pre-trained model? e.g insert a new conv in the middle of Resnet’s bottelneck.
There’s no easy way to insert a new layer in the middle of an existing model as far as I’m aware. A definite solution is to build the structure that you want in a new class and then copy the corresponding weights over from the pretrained model.
After loading model，we can directly specify model.conv_x = nn.Sequential([new_layer, model.conv_x]), by this way, we can still use thepretrained model.conv_x
Can you help a newbie like me. I import pretrained resnest34 as:
resnet = models.resnet34(pretrained=True)
Now I want to insert a conv2d 1x1 kernel layer before the fc to increase channel size from 512 to 6000 and then add a fc 6000 x 6000
I am so new to pytorch that I need some hand-holding. Can you write the lines of code needed? I am still at monkey-see monkey-learn stage. Thanks in anticipation
I think the easiest approach would be to derive from
ResNet and add your layers.
This should do what you need:
class MyResnet2(models.ResNet): def __init__(self, block, layers, num_classes=1000): super(MyResnet2, self).__init__(block, layers, num_classes) self.conv_feat = nn.Conv2d(in_channels=512, out_channels=6000, kernel_size=1) self.fc = nn.Linear(in_features=6000, out_features=6000) def forward(self, x): x = self.conv1(x) x = self.bn1(x) x = self.relu(x) x = self.maxpool(x) x = self.layer1(x) x = self.layer2(x) x = self.layer3(x) x = self.layer4(x) x = self.avgpool(x) x = self.conv_feat(x) x = x.view(x.size(0), -1) x = self.fc(x) return x from torchvision.models.resnet import BasicBlock model = MyResnet2(BasicBlock, [3, 4, 6, 3], 1000) x = Variable(torch.randn(1, 3, 224, 224)) output = model(x)
Note that the shape of
x= self.avgpool(x) is already
[batch, 512, 1, 1] for
x.shape = [batch, 3 ,224, 224].
You could therefore flatten
x and just use two
Linear layers, since it would be the same as a
Thank you sir!,
Now a if I re-read some of the tutorials, they will register in my head.
Sorry for being so late to reply. My way should be replace ‘Resnet.fc = nn.Linear(512, num_classes)’ with ‘Resnet.fc = nn.Sequential(nn.Conv2d(512, 6000), nn.Linear(6000,6000))’
Using this approach you would have to define a
Flatten layer, since it will crash in the
class Flatten(nn.Module): def __init__(self): super(Flatten, self).__init__() def forward(self, x): x = x.view(x.size(0), -1) return x seq = nn.Sequential(nn.Conv2d(512, 6000, 1), Flatten(), nn.Linear(6000,6000)) x = Variable(torch.randn(1, 512, 1, 1)) seq(x)