GradCAM in PyTorch

In this article, we are going to learn how to plot GradCam [1] in PyTorch. To get the GradCam outputs, we need the activation maps and the gradients of those activation maps. Let us jump straight into the code!! We are going to use hooks to get the activation maps and the gradients from the desired layer and tensor, respectively. For this tutorial, we are going to take the activation maps from layer4 of ResNet50 and gradients with respect to the output tensor of the same.