# Since both RoI Align and PrRoI Pooling use bilinear interpolation, why is RoI Align discrete while PrRoI Pooling continuous?

I have two questions.

1. Since both use bilinear interpolation, why is RoI Align discrete while PrRoI Pooling continuous?

1. Could anyone explain the intuition behind the derivative of PrPool()?

• Can you please ask only one question per post? If you have two questions, ask each of them in its separate post. This not only allows people to focus on one problem at a time but it will make posts more useful for future readers, given that, often, readers don't have the same combination of problems. – nbro Aug 1 at 11:55