Architecture of the Component Collective Messaging Interface.
ABSTRACT Different programming paradigms utilize a variety of collective communication operations, often with different semantics. We present the component collective messaging interface (CCMI) that can support asynchronous non-blocking collectives and is extensible to different programming paradigms and architectures. CCMI is designed with components written in the C++ programming language, allowing it to be reusable and extendible. Collective algorithms are embodied in topological schedules and executors that execute them. Portability across architectures is enabled by the multisend data movement component. CCMI includes a programming language adaptor used to implement different APIs with different semantics for different paradigms. We study the effectiveness of CCMI on 16K nodes of Blue Gene/P machine and evaluate its performance for the barrier, broadcast, and allreduce collective operations and several application benchmarks. We also present the performance of the barrier collective on the Abe Infiniband cluster.
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Conference Paper: A configurable algorithm for parallel image-compositing applications.[Show abstract] [Hide abstract]
ABSTRACT: Collective communication operations can dominate the cost of large-scale parallel algorithms. Image compositing in parallel scientific visualization is a reduction operation where this is the case. We present a new algorithm called Radix-k that in many cases performs better than existing compositing algorithms. It does so through a set of configurable parameters, the radices, that determine the number of communication partners in each message round. The algorithm embodies and unifies binary swap and direct-send, two of the best-known compositing methods, and enables numerous other configurations through appropriate choices of radices. While the algorithm is not tied to a particular computing architecture or network topology, the selection of radices allows Radix-k to take advantage of new supercomputer interconnect features such as multiporting. We show scalability across image size and system size, including both powers of two and nonpowers-of-two process counts.Proceedings of the ACM/IEEE Conference on High Performance Computing, SC 2009, November 14-20, 2009, Portland, Oregon, USA; 01/2009
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ABSTRACT: The implementation and optimization of collective communication operations is an important field of active research. Such operations directly influence application performance and need to map the communication requirements in an optimal way to steadily changing network architectures. In this work, we define an abstract domain-specific language to express arbitrary group communication operations. We show the universality of this language and how all existing collective operations can be implemented with it. By design, it readily lends itself to blocking and nonblocking execution, as well as to off-loaded execution of complex group communication operations. We also define several offline and online optimizations (compiler transformations and scheduling decisions, respectively) to improve the overall performance of the operation. Performance results show that the overhead to express current collective operations is negligible in comparison to the potential gains in a highly optimized implementation.ICPP 2009, International Conference on Parallel Processing, Vienna, Austria, 22-25 September 2009; 01/2009
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ABSTRACT: Nonblocking collective communication operations are currently being considered for inclusion into the MPI stan- dard and are an area of active research. The benefits of such operations are documented by several recent publications, but so far, research concentrates on InfiniBand clusters. This paper describes an implementation of nonblocking collectives for clusters with the Scalable Coherent Interface (SCI) interconnect. We use synthetic and application kernel benchmarks to show that with nonblocking functions for collective communication performance enhancements can be achieved on SCI systems. Our results indicate that for the implementation of these nonblocking collectives data trans- fer methods other than those usually used for the blocking version should be considered to realize such improvements.23rd IEEE International Symposium on Parallel and Distributed Processing, IPDPS 2009, Rome, Italy, May 23-29, 2009; 01/2009