[BUG] mpi_comms comm_split does not split NCCL communicator
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bug
inactive-30d
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- Dominant language
- Cuda
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Description
https://github.com/rapidsai/raft/blob/branch-0.16/cpp/include/raft/comms/mpi_comms.hpp#L136
std::unique_ptr<comms_iface> comm_split(int color, int key) const {
MPI_Comm new_comm;
MPI_TRY(MPI_Comm_split(mpi_comm_, color, key, &new_comm));
return std::unique_ptr<comms_iface>(new mpi_comms(new_comm, true));
}
mpi_comms uses MPI for P2P and NCCL for collectives, but it split only MPI communicator in comm_split.
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- Read the whole issue, then the project's contributing guide.
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- Open a pull request that references the issue number.
Research direction
Start in cpp/include/raft/comms/mpi_comms.hpp at the comm_split implementation shown in the issue, then trace how mpi_comms stores and initializes its MPI and NCCL communicators. Update the split behavior so both communicators represent the requested partition, and verify that the resulting communicator is usable for MPI point-to-point and NCCL collective operations.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- distributed-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100