Sliding Window Allreduce Stubs

[nsarka]

This PR (1 out of 2 PRs) defines the structs and function stubs for sliding window allreduce. It also adds a gtest for the algorithm. The next PR will have the function implementations.

@janjust @manjugv @samnordmann @Sergei-Lebedev

[swx-jenkins3]

Can one of the admins verify this patch?

[janjust]

Let's fix exposing internal structs, then should be good to go

[samnordmann]

Thank you for the PR, it looks good to me. I only left minor comments mostly on the tests

[nsarka]

Hi @samnordmann , I have updated the review with your comments.

[samnordmann]

Hi @samnordmann , I have updated the review with your comments.

I'm seeing that many comments are not addressed. Also, the CI needs to be green. Please, can you re-request for review through github when it is ready ?

[samnordmann]

LGTM!

[janjust]

@Sergei-Lebedev whenever you get a chance, could you review?

[janjust]

@Sergei-Lebedev we've removed the ep array ptr, in the follow up we'll just us a macro for a cleaner implementation, but we're going to rely on the hash look up (if it comes back to be less performant, we can make the change then and provide data).

Whenever you can, please give it a quick look - I'm very eager to get this in so we can open up follow up

[Sergei-Lebedev]

@Sergei-Lebedev we've removed the ep array ptr, in the follow up we'll just us a macro for a cleaner implementation, but we're going to rely on the hash look up (if it comes back to be less performant, we can make the change then and provide data).

Whenever you can, please give it a quick look - I'm very eager to get this in so we can open up follow up

Thanks, LGTM, please fix few minor comments