Use INFO instead of WARNING for an unused graph input.

[skottmckay]

An unused graph input doesn't hurt anything so use INFO rather than WARNING so the message doesn't show up with the default output level of WARNING.

[snnn]

It indicated the model is somehow wrong. But, now , we get this warning because of our internal graph transformers. We should fix the problem, instead of ignore the warning.

[skottmckay]

It indicated the model is somehow wrong. But, now , we get this warning because of our internal graph transformers. We should fix the problem, instead of ignore the warning.

The constant folding actually relies on the cleanup of unused initializers in graph.cc so it's expected that there would be things to remove making 'warning' too sever in that case. That could be refactored though.

In other cases, whilst the model could have these unused things removed, is it 'wrong' or just sub-optimal?

[kkaranasos]

I think it would be great to add a RemoveInitializerIfUnused method, and use it in multiple transformers (constant folding; but also in some fusions eventually as long as we don't update initializers in place, there is an ongoing discussion about that). It might also help with releasing memory gradually.
But either way, it doesn't seem to me that unused initializers should be a warning.

[snnn]

Without enabling the transformers, we only saw this warning in very a few models (<1%). The message indicates the converter should be improved, to not leave garbage in the model.

[askhade]

It indicated the model is somehow wrong. But, now , we get this warning because of our internal graph transformers. We should fix the problem, instead of ignore the warning.

The constant folding actually relies on the cleanup of unused initializers in graph.cc so it's expected that there would be things to remove making 'warning' too sever in that case. That could be refactored though.

In other cases, whilst the model could have these unused things removed, is it 'wrong' or just sub-optimal?

In my opinion, other cases (non transformer related) where we see these unused inputs or initializers - it is not wrong... it is sub-optimal. It would be wrong if it affects the correctness... That said we should fix converters to remove any unused initializer\input.

Right now this change looks good to me. Later we can implement the change to gradually release the memory instead of waiting till the end. This will not only eliminate such logs but it will also alleviate the peak memory increase issue.