SCHEDULE: NOV 10-16, 2012
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Optimization Principles for Collective Neighborhood Communications
SESSION: Communication Optimization
EVENT TYPE: Papers
TIME: 4:00PM - 4:30PM
SESSION CHAIR: Ron Brightwell
AUTHOR(S):Torsten Hoefler, Timo Schneider
Many scientific applications work in a bulk-synchronous mode of iterative communication and computation steps. Even though the communication steps happen at the same time, important patterns such as stencil computations cannot be expressed as collective communications in MPI. Neighborhood collective operations allow to specify arbitrary collective communication relations during runtime and enable optimizations similar to traditional collective calls. We show a number of optimization opportunities and algorithms for different communication scenarios. We also show how users can assert additional constraints that provide new optimization opportunities in a portable way. Our communication and protocol optimizations result in a performance improvement of up to a factor of two for stencil communications. We found that our optimization heuristics can automatically generate communication schedules that are comparable to hand-tuned collectives. With those optimizations, we are able to accelerate arbitrary collective communication patterns, such as regular and irregular stencils with optimization methods for collective communications.
Ron Brightwell (Chair) - Sandia National Laboratories
Torsten Hoefler - University of Illinois at Urbana-Champaign
Timo Schneider - University of Illinois at Urbana-Champaign