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We investigate the use of the derived datatype mechanism of MPI (the Message-Passing Interface) in the implementation of the classic all-to-all communication algorithm of Bruck et al.\ (1997). Through a series of improvements to the canonical implementation of the algorithm we gradually eliminate initial and final processor-local data reorganizations,(More)
We propose a specification and discuss implementations of collective operations for parallel stencil-like computations that are not supported well by the current MPI 3.1 neighborhood collectives. In our isomorphic, sparse collectives all processes partaking in the communication operation use similar neighborhoods of processes with which to exchange data.(More)
It is a desirable feature of MPI that application specific collective operations can be implemented efficiently in terms of other, more primitive operations of MPI. Recent MPI 3.0 functionality makes it possible to build portable libraries that are sensitive to and can exploit the hierarchical structure of, e.g., current shared-memory clusters, and thus in(More)
With recent MPI 3.0 functionality for creating communicators that partly reflects the hierarchy of standard clusters of shared-memory nodes, hierarchical, collective algorithms can more conveniently be implemented by combinations of other collective MPI operations. On systems that support MPI 3.0, with MPI_Alltoall as a concrete example, we show that(More)
—Isomorphic (sparse) collective communication is a form of collective communication in which all involved processes communicate in small, identically structured neighborhoods of other processes. Isomorphic neighborhoods are defined via an embedding of the processes in a regularly structured topology, e.g., d-dimensional torus, which may correspond to the(More)
A monitoring programme was established in order to support community-based seaweed farming in south-west Madagascar by providing scientific information on the effects of physico-chemical and health factors influencing the growth of Kappaphycus alvarezii (cottonii). Six aquaculture site configurations were studied. These consisted of high and low flow(More)
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