About the input image size

[xxx2974]

Hello，If the input image size resized to 512×256，it will report an error. So the height to width ratio is can only be 3:1? If I want a size of 512×256，what should I do？

The error：
Traceback (most recent call last):
File "script/experiment/train_pcb.py", line 498, in
main()
File "script/experiment/train_pcb.py", line 436, in main
_, logits_list = model_w(ims_var)
File "/home/xiaozhenzhen/anaconda2/envs/pytorch-PCB/lib/python2.7/site-packages/torch/nn/modules/module.py", line 325, in call
result = self.forward(*input, **kwargs)
File "/home/xiaozhenzhen/anaconda2/envs/pytorch-PCB/lib/python2.7/site-packages/torch/nn/parallel/data_parallel.py", line 68, in forward
outputs = self.parallel_apply(replicas, inputs, kwargs)
File "/home/xiaozhenzhen/anaconda2/envs/pytorch-PCB/lib/python2.7/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/xiaozhenzhen/anaconda2/envs/pytorch-PCB/lib/python2.7/site-packages/torch/nn/parallel/parallel_apply.py", line 67, in parallel_apply
raise output
AssertionError

[huanghoujing]

You have to make sure that image_height / 16 % 6 == 0. When your image height is 512, 512. / 16 % 6 is 2. This requirement is to make sure that height of Conv5 feature map should be evenly divided by number of stripes (the default stripe number is 6). The detail in code is here.

[xxx2974]

Thanks a lot. I know the number 6 what means, but what's the mean of the number 16?

[huanghoujing]

If you set last conv stride of ResNet-50 to 1, the final feature map size is image_height / 16, image_width / 16 (this is the case of PCB); If you set last conv stride of ResNet-50 to 2, the final feature map size is image_height / 32, image_width / 32.

[xxx2974]

I see, thank you very much. I will take a careful look.