I want to use the MPI_Allreduce to synchronize results from all the processes: https://github.com/open-mpi/ompi/blob/master/ompi/mpi/c/allreduce.c But I want to know the background algorithm to implement Allreduce. When I check the coll base of MPI_Allreduce: https://github.com/open-mpi/ompi/blob/2ae3cfd9bc9aa8cab80986a1921fd7ad9d198d07/ompi/mca/coll/base/coll_base_allreduce.c There are implementations like: ompi_coll_base_allreduce_intra_nonoverlapping, ompi_coll_base_allreduce_intra_recursivedoubling, ompi_coll_base_allreduce_intra_ring..etc. So how can I know which exact implement I am using when I use MPI_Allreduce. Or can I configure these? For example, I only want to use ring allreduce. How should I configure it?
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