Intersecting pooling regions in RoI layer

[hermanzdosilovic]

Hi @rbgirshick,

I've read your RoI pooling implementation and found it very interesting that pooling regions in one RoI overlap.

Let's say that we have one one channel feature map 5x5 and that we have only one RoI (0, 0, 4, 4) with pooled_height_ and pooled_width_ set to 2. Current implementation makes 4 pools in 4 regions and each region is of size 3x3 and the common element of those 4 pool regions is element (2,2).

Is this expected behaviour? Should pooled regions overlap? Why is that prefered? I've read this article where thats not the case and that's why I am confused with your implementation.

BR,
Herman