NarineK
commented
4 years ago Hi Avanti, thank you so much for the feedback, that's a great point! Now, I remember that I read about it in your paper a while ago.
Since this is a Toy model, I didn't pay attention to the last layer but it is a good point. I will update either the documentation or the examples in getting started
Currently, DeepLift's implementations doesn't support intermediate layers or neurons but we can easily do it with a forward hook. Due to time constraints we haven't added it in the release but we will make it available in the master branch soon.
Thank you so much! We really value your feedback 👍
orionr
gabrieltseng
Often, in practice, we wish to compute the contributions w.r.t. the logits of the final sigmoid/softmax, rather than w.r.t. the final network output itself. This is to avoid artifacts that can be caused by the saturating nature of the sigmoid/softmax, and comes into play when comparing attributions between examples. It is particularly relevant if gradient*input is used as an attribution method, because for examples with very confident predictions, the sigmoid/softmax outputs tend to saturate and the gradients will approach zero. I'm wondering if it may be worth mentioning this in the documentation - in the current "getting started", the toy model has a sigmoid output:
I'm concerned that a naive user may try to compare the magnitudes of attributions across different examples without realizing that, for sigmoid/softmax outputs, it may be worth removing the final nonlinearity before doing such a comparison. We discuss this in Section 3.6 of the deeplift paper. Ideally there would be an option in Captum to ignore the final nonlinearity, but I realize it may not be trivial to add that option. Sorry if this is already addressed and I missed it.