Discamus continentiam augere, luxuriam coercere
Home -> Publications
all years
    edited volumes
  Full CV [pdf]


  Past Events

Publications of Torsten Hoefler
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.

T. Hoefler, J. Squyres, W. Rehm and A. Lumsdaine:

 A Case for Non-Blocking Collective Operations

(Vol 4331/2006, In Frontiers of High Performance Computing and Networking - ISPA'06 Workshops, presented in Sorrento, Italy, pages 155-164, Springer Berlin / Heidelberg, ISBN: 978-3-540-49860-5, Dec. 2006)


Non-blocking collective operations for MPI have been in discussion for a long time. We want to contribute to this discussion and to give a rationale for the usage these operations and assess their possible benefits. A LogGP model for the CPU overhead of collective algo- rithms and a benchmark to measures it are provided and show a large potential to overlap communication and computation. We show that non-blocking collective operations can provide at least the same benefits as non-blocking point to point operations already do. Our claim is that actual CPU overhead for non-blocking collective operations depends on the message size and the communicator size and benefits especially highly scalable applications with huge communicators. We prove that the share of the overhead of the overall communication time of current blocking collective operations gets smaller with bigger communicators and larger messages. We show that the user level CPU overhead is less than 10% for MPICH2 and LAM/MPI using TCP/IP communication, which leads us to the conclusion that, by using non-blocking collective communication, ideally 90% idle CPU time can be freed for the application.


download article:


  author={T. Hoefler and J. Squyres and W. Rehm and A. Lumsdaine},
  title={{A Case for Non-Blocking Collective Operations}},
  booktitle={Frontiers of High Performance Computing and Networking - ISPA'06 Workshops},
  location={Sorrento, Italy},
  publisher={Springer Berlin / Heidelberg},

serving:© Torsten Hoefler