* Update graphsage multi-gpu example to use mutliple GPUs for validation and
testing.
* Remove argmax
* Fix rebase error
* Add more documentation to example and simplify
* Switch to name shared memory
* Add comment about how training is distributed
* Restore iteration count
* fix munmap error reporting for better error messages
Co-authored-by: Quan (Andy) Gan <coin2028@hotmail.com>
* huuuuge update
* remove
* lint
* lint
* fix
* what happened to nccl
* update multi-gpu unsupervised graphsage example
* replace most of the dgl.mp.process with torch.mp.spawn
* update if condition for use_uva case
* update user guide
* address comments
* incorporating suggestions from @jermainewang
* oops
* fix tutorial to pass CI
* oops
* fix again
Co-authored-by: Xin Yao <xiny@nvidia.com>