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Publications of SPCL
|T. Hoefler and T. Schneider:|
|Communication-Centric Optimizations by Dynamically Detecting Collective Operations|
(. Vol , Nr. , In Proceedings of the 17th ACM symposium on Principles and practice of parallel programming, presented in , pages , , ISSN: , ISBN: , Feb. 2012, (poster paper) )
AbstractThe steady increase of parallelism in high-performance computing platforms implies that communication will be most important in large-scale applications. In this work, we tackle the problem of transparent optimization of large-scale communication patterns using online compilation techniques. We utilize the Group Operation Assembly Language (GOAL), an abstract parallel dataflow definition language, to specify our transformations in a device-independent manner. We develop fast schemes that analyze data-flow and synchronization semantics in GOAL and detect if parts of the (or the whole) communication pattern express a known collective communication operation. The detection of collective operations allows us to replace the detected patterns with highly optimized algorithms or low-level hardware calls and thus improve performance significantly. Benchmark results suggest that our technique can lead to a performance improvement of orders of magnitude compared with various optimized algorithms written in Co-Array Fortran. Detecting collective operations also improves the programmability of parallel languages in that the user does not have to understand the detailed semantics of high-level communication operations in order to generate efficient and scalable code.