We present a support function for MPI derived datatypes on an Enhancer of Memory and Network named DIMMnet-3 which is under development. Semi-hardwired derived datatype communication based on RDMA with hardwired gather and scatter is proposed. This mechanism and MPI using it are implemented on DIMMnet-2 which is a former prototype. The performance of gather or scatter transfer of 8byte elements with large interval by using vector commands of DIMMnet-2 is 6.8 compared with software on a host. Proprietary benchmark of MPI derived datatype communication for transferring a submatrix corresponding to a narrow HALO area is executed. Observed bandwidth on DIMMnet-2 is far higher than that for similar condition with VAPI based MPI implementation on Infiniband, even though poorer CPU and motherboard are used.
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