Is it possible to implement Spatial Pyramid Pooling (SPP) layer in PyTorch only, without using C/CUDA code?
A SPP layer essentially needs to pool over a variably-sized feature map into a fix-sized feature map.  For instance, a SPP layer with a single output size 22 would pool over a 66 feature map by 33 windows, and over a 88 map by 4*4 windows.