Copyright Notice:

The documents distributed by this server have been provided by the contributing authors as a means to ensure timely dissemination of scholarly and technical work on a noncommercial basis. Copyright and all rights therein are maintained by the authors or by other copyright holders, notwithstanding that they have offered their works here electronically. It is understood that all persons copying this information will adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

Publications of SPCL

T. Hoefler and J. L. Traeff:

 Sparse Collective Operations for MPI

(. Vol , Nr. , In Proceedings of the 23rd IEEE International Parallel & Distributed Processing Symposium, HIPS'09 Workshop, presented in Rome, Italy, pages , , ISSN: 1530-2075, ISBN: 978-1-4244-3750-4, May 2009)


We discuss issues in designing sparse (nearest neighbor) collective operations for communication and reduction operations in small neighborhoods for the Message Passing Interface (MPI). We propose three such operations, namely a sparse gather operation, a sparse all-to-all, and a sparse reduction operation in both regular and irregular (vector) variants. By two simple experiments we show a) that a collective handle for message scheduling and communication optimization is necessary for any such interface, b) that the possibly different amount of communication between neighbors need to be taken into account by the optimization, and c) illustrate the improvements that are possible by schedules that posses global information compared to implementations that can rely on only local information. We discuss different forms the interface and optimization handles could take. The paper is inspired by current discussion in the MPI Forum.


download article:
download slides:


  author={T. Hoefler and J. L. Traeff},
  title={{Sparse Collective Operations for MPI}},
  booktitle={Proceedings of the 23rd IEEE International Parallel \& Distributed Processing Symposium, HIPS'09 Workshop},
  location={Rome, Italy},