An Evaluation of OpenSHMEM Interfaces for the Variable-Length Alltoallv() Collective Operation, In: OpenSHMEM and Related Technologies. Experiences, Implementations, and Technologies

Conference · Thu Jan 01 00:00:00 EST 2015

DOI:https://doi.org/10.1007/978-3-319-26428-8_6· OSTI ID:1567383

Lopez, M. Graham ^[1]; Shamis, Pavel ^[1]; Venkata, Manjunath Gorentla ^[1]

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1. Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

Alltoallv() is a collective operation which allows all processes to exchange variable amounts of data with all other processes in the communication group. This means that Alltoallv() requires not only O(N2) communications, but typically also additional exchanges of the data lengths that will be transmitted in the eventual Alltoallv() call. This pre-exchange is used to calculate the proper offsets for the receiving buffers on the target processes. However, we propose two new candidate interfaces for Alltoallv() that would mitigate the need for the user to set up this extra exchange of information at the possible cost of memory efficiency. We explain the new interface variants and show how a single call can be used in place of the traditional Alltoall()/ Alltoallv() pair. We then discuss the performance tradeoffs for overall communication and memory costs, as well as both software and hardware-based optimizations and their applicability to the various proposed interfaces.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1567383
• Resource Relation: Conference: Workshop on OpenSHMEM and Related Technologies, Annapolis, MD, March 4-6, 2014
• Country of Publication: United States
• Language: English

Related Subjects

Computer Science