Parallel sorting by regular sampling
Journal of Parallel and Distributed Computing
Scaling an optimistic parallel simulation of large-scale interconnection networks
WSC '05 Proceedings of the 37th conference on Winter simulation
Exascale algorithms for generalized MPI_comm_split
EuroMPI'11 Proceedings of the 18th European MPI Users' Group conference on Recent advances in the message passing interface
Parallel sorting with minimal data
EuroMPI'11 Proceedings of the 18th European MPI Users' Group conference on Recent advances in the message passing interface
SC '12 Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis
Scalable algorithms for constructing balanced spanning trees on system-ranked process groups
EuroMPI'12 Proceedings of the 19th European conference on Recent Advances in the Message Passing Interface
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Existing algorithms for creating communicators in MPI programs will not scale well to future exascale supercomputers containing millions of cores. In this work, we present a novel communicator-creation algorithm that does scale well into millions of processes using three techniques: replacing the sorting at the end of MPI_Comm_split with merging as the color and key table is built, sorting the color and key table in parallel, and using a distributed table to store the output communicator data rather than a replicated table. This reduces the time cost of MPI_Comm_split in the worst case we consider from 22 seconds to 0.37 second. Existing algorithms build a table with as many entries as processes, using vast amounts of memory. Our algorithm uses a small, fixed amount of memory per communicator after MPI_Comm_split has finished and uses a fraction of the memory used by the conventional algorithm for temporary storage during the execution of MPI_Comm_split.