https://asplos.dev/wordpress/2020/02/12/%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8nccl-%ef%bc%88%e6%9b%b4%e5%a5%bd%e7%9a%84%ef%bc%89%e4%bb%a3%e6%9b%bfmpi%ef%bc%88rdma%ef%bc%89/