Here the filter is not flipped, so it is a cross correlation rather than a convolution operation?
Yes, you are correct, this operation is defined as cross-correlation in math but called ‘convolution’ in DNN by convention. I remember in one video of C4 Andrew mentioned about the different definitions of ‘convolution’ between math-book and ML literature.
Thank you for clarifying. It is the first time I know convolution is not convolution in DNN . I think we should call CNN as cross-correlation neural networks