Opened an issue on FAISS to avoid code duplication : facebookresearch/faiss#2097.

Using a custom memory manager in FAISS currently requires overriding methods of GpuResources and GpuResourcesProvider classes. Most of the logic however, is consistent with existing StandardGpuResourcesImpl and StandardGpuResources classes causing unnecessary and difficulty maintainable rewrites.

It would be possible to prevent consequent rewrites thanks to updates to the StandardGpuResources.h header file. Indeed the ideal situation would be to inherit the logic of these classes and only override the allocMemory and deallocMemory methods.

The necessary changes would be the following :

1. Promote attributes from private to protected
2. Use allocMemory in initializeForDevice to prevent cudaHostAlloc call
3. (optionally) Remove unnamed namespace to allow the reuse of the allocsToString function

@viclafargue, I looked back over my last comment and realized it was fairly ambiguous. I think having the comment on this PR is very useful as well but we should also have the comment in the code, preferably at the top of faiss_mr.hpp

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@viclafargue it's been a little while so just wanted to check the status on this PR. IIRC, we are waiting on cuml side to pass successfuly, right?

@viclafargue it's been a little while so just wanted to check the status on this PR. IIRC, we are waiting on cuml side to pass successfuly, right?

Thanks for reminding me of this. Yes, I just solved the merge conflicts on this PR.

@gpucibot merge