SC12 Home > SC12 Schedule > SC12 Presentation - Mapping Applications with Collectives over Sub-Communicators on Torus Networks

SCHEDULE: NOV 10-16, 2012

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Mapping Applications with Collectives over Sub-Communicators on Torus Networks

SESSION: Communication Optimization

EVENT TYPE: Papers

TIME: 3:30PM - 4:00PM

SESSION CHAIR: Ron Brightwell

AUTHOR(S):Abhinav Bhatele, Todd Gamblin, Steven H. Langer, Peer-Timo Bremer, Erik W. Draeger, Bernd Hamann, Katherine E. Isaacs, Aaditya G. Landge, Joshua A. Levine, Valerio Pascucci, Martin Schulz, Charles H. Still

ROOM:255-EF

ABSTRACT:
The placement of tasks in a parallel application on specific nodes of a supercomputer can significantly impact performance. Traditionally, task mapping has focused on reducing the distance between communicating processes on the physical network. However, for applications that use collectives over sub-communicators, this strategy may not be optimal. Many collectives can benefit from an increase in bandwidth even at the cost of an increase in hop count, especially when sending large messages. We have developed a tool, Rubik, that provides a simple API to create a wide variety of mappings for structured communication patterns. Rubik supports several operations that can be combined into a large number of unique patterns. Each mapping can be applied to disjoint groups of MPI processes involved in collectives to increase the effective bandwidth. We demonstrate the use of these techniques for improving performance of two parallel codes, pF3D and Qbox, which use collectives over sub-communicators.

Chair/Author Details:

Ron Brightwell (Chair) - Sandia National Laboratories

Abhinav Bhatele - Lawrence Livermore National Laboratory

Todd Gamblin - Lawrence Livermore National Laboratory

Steven H. Langer - Lawrence Livermore National Laboratory

Peer-Timo Bremer - Lawrence Livermore National Laboratory

Erik W. Draeger - Lawrence Livermore National Laboratory

Bernd Hamann - University of California, Davis

Katherine E. Isaacs - University of California, Davis

Aaditya G. Landge - University of Utah

Joshua A. Levine - University of Utah

Valerio Pascucci - University of Utah