Talks and Poster Presentations (with Proceedings-Entry):
J. Träff, A. Rougier:
"Zero-copy, Hierarchical Gather is not possible with MPI Datatypes and Collectives";
Talk: 21st European MPI Users' Group Meeting, EuroMPI/ASIA 2014,
- 2014-09-12; in: "Proceedings of the 21st European MPI Users' Group Meeting",
J. Dongarra, Y. Ishikawa, A. Hori (ed.);
New York, NY, USA
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 principle to implement efficient, hierarchy-aware collective operations effectively.
In this paper, which complements investigations on all-to-all communication, we show that current MPI 3.0 functionality is insufficient to implement simple, collective gather operations as found in the MPI standard in a hierarchical manner in terms of simpler gather operations, if we pose the extra constraint that no explicit data reorganization apart from what can be expressed with MPI derived datatypes is allowed in any stage of the implementation. Thus, we establish that zero-copy, hierarchical implementations of MPI_Gather are not possible in current MPI. We discuss ways to alleviate the problems, and sketch a possible solution.
"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
Created from the Publication Database of the Vienna University of Technology.