[FEATURE] Effective drop path.

[leng-yue]

Is your feature request related to a problem? Please describe.

While current drop path implementation in TIMM doesn't save computation resources, implementing a true drop path that ignores unnecessary tokens will significantly speed up training when path drop ratio is high (e.g. 0.3 or 0.4).

Describe the solution you'd like
Reference to: https://github.com/facebookresearch/dinov2/blob/c3c2683a13cde94d4d99f523cf4170384b00c34c/dinov2/layers/block.py#L110

I already implemented a modified Block that utilizes this function and it gives me a huge performance improvement. I can add it to PR #1835 if it's a good idea.

[rwightman]

@leng-yue I noticed that, but # the overhead is compensated only for a drop path rate larger than 0.1 suggested the impact isn't that great if you need at least 0.1 for it to be break even? doesn't seem worth the added complexity, can it be better quantified?

[leng-yue]

The ratio in dinov2's paper is 0.3 or 0.4. In our test, using their Drop Path implementation can make the training 15% faster when the ratio is 0.3. I can do a benchmark if you want.

[leng-yue]

https://colab.research.google.com/drive/1ydeHogHNlGgVYCFBbgd4a5PYi9LZWHLH?usp=sharing

As this benchmark shows, when dpr is 0.4, it can save 41% of the time when training.

[leng-yue]

Any suggestion?

[rwightman]

@leng-yue sorry I've got quite a few other tasks to plow through so haven't had a chance to look more closely at this, I do want to test and weight the added complexity vs benefit before making final decisions

[leng-yue]

Maybe adding it as a new Block is better? So that it won't have negative effects to existing codes.

[rwightman]

@leng-yue yeah, I suppose a new Block would mitigate risk concerns for now, and also fix the breakage of other blocks that don't current support it. Can figure out how to make it easier to select later...

[leng-yue]

I will implement it later.

[leng-yue]

Updated.