Input size mismatch error when retraining inceptionV3 model

[sambasivapentyala]

I'm facing trouble when training a model using pre-trained inceptionV3 for my own image data set.

I'm loading images using data.Dataset loader and 'transforms' for image transformation.

Here's my inceptionV3 model

inceptionV3 = torchvision.models.inception_v3(pretrained=True)
pretrained_model = nn.Sequential(*list(inceptionV3.children()))
pretrained_model = nn.Sequential(*list(pretrained_features.children())[:-1])
for param in pretrained_model.parameters(): param.requires_grad = False

Here's my transforms code

data_transforms = transforms.Compose([
transforms.Scale((299,299)),
transforms.RandomHorizontalFlip(),
transforms.ToTensor(),
transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])
])

I'm getting this error at the line 'out_features = pretrained_model(inputs)'

Traceback (most recent call last): File "build_models.py", line 42, in <module> use_gpu=use_gpu) File "/home/ubuntu/apparel-styles/ml_src/classifiers.py", line 488, in create_attributes_model batch_size, num_workers, num_epochs, use_gpu=use_gpu) File "/home/ubuntu/apparel-styles/ml_src/classifiers.py", line 276, in train_model flatten_pretrained_out=flatten_pretrained_out) File "/home/ubuntu/apparel-styles/ml_src/classifiers.py", line 181, in train_attribute_model out_features = pretrained_model(inputs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/modules/module.py", line 325, in __call__ result = self.forward(*input, **kwargs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/parallel/data_parallel.py", line 68, in forward outputs = self.parallel_apply(replicas, inputs, kwargs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/parallel/data_parallel.py", line 78, in parallel_apply return parallel_apply(replicas, inputs, kwargs, self.device_ids[:len(replicas)]) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/parallel/parallel_apply.py", line 67, in parallel_apply raise output File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/parallel/parallel_apply.py", line 42, in _worker output = module(*input, **kwargs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/modules/module.py", line 325, in __call__ result = self.forward(*input, **kwargs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/modules/container.py", line 67, in forward input = module(input) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/modules/module.py", line 325, in __call__ result = self.forward(*input, **kwargs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torchvision/models/inception.py", line 312, in forward x = self.fc(x) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/modules/module.py", line 325, in __call__ result = self.forward(*input, **kwargs) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/modules/linear.py", line 55, in forward return F.linear(input, self.weight, self.bias) File "/home/ubuntu/apparel-styles/env/venv/lib/python3.6/site-packages/torch/nn/functional.py", line 835, in linear return torch.addmm(bias, input, weight.t()) RuntimeError: size mismatch at /pytorch/torch/lib/THC/generic/THCTensorMathBlas.cu:243

After getting this error, I tried to print the input size. It's value is

print(inputs.shape)

  torch.Size([256, 3, 299, 299])

[fmassa]

The problem might be that inception does not follow exactly a Sequential module because of the AuxLogits classifier, which makes your model not match the original inception.
I think it might be easier in your case to just modify the fc layer to be of the dimension you want.

inceptionV3 = torchvision.models.inception_v3(pretrained=True)
inceptionV3.fc = nn.Linear(2048, num_classes)