To improve productivity for developing parallel applications on high performance computing systems, the XcalableMP PGAS language has been proposed. XcalableMP supports both a typical parallelization under the ''global-view memory model'' which uses directives and a flexible parallelization under the ''local-view memory model'' which uses coarray features. The goal of the present paper is to clarify XcalableMP's productivity and performance. To do so, we implement and evaluate the high performance computing challenge benchmark, namely, EP STREAM Triad, High Performance Linpack, Global fast Fourier transform, and RandomAccess on the K computer using up to 16,384 compute nodes and a generic cluster system using up to 128 compute nodes. We found that we could more easily implement the benchmarks using XcalableMP rather than using MPI. Moreover, most of the performance results using XcalableMP were almost the same as those using MPI.
SUMMARYThis paper presents a set of extensions on High Performance Fortran (HPF) to make it more usable for parallelizing real-world production codes. HPF has been effective for programs that a compiler can automatically optimize efficiently. However, once the compiler cannot, there have been no ways for the users to explicitly parallelize or optimize their programs. In order to resolve the situation, we have developed a set of HPF extensions (HPF/JA) to give the users more control over sophisticated parallelization and communication optimizations. They include parallelization of loops with complicated reductions, asynchronous communication, user-controllable shadow, and communication pattern reuse for irregular remote data accesses. Preliminary experiments have proved that the extensions are effective at increasing HPF's usability.
SUMMARYVPP Fortran is a data parallel language that has been designed for the VPP series of supercomputers. In addition to pure data parallelism, it contains certain low-level features that were designed to extract high performance from user programs. A comparison of VPP Fortran and High-Performance Fortran (HPF) 2.0 shows that these low-level features are not available in HPF 2.0. The features include asynchronous interprocessor communication, explicit shadow, and the LOCAL directive. They were shown in VPP Fortran to be very useful in handling real-world applications, and they have been included in the HPF/JA extensions. They are described in the paper. The HPF/JA Language Specification Version 1.0 is an extension of HPF 2.0 to achieve practical performance for real-world applications and is a result of collaboration in the Japan Association for HPF (JAHPF). Some practical programming and tuning procedures with the HPF/JA Language Specification are described, using the NAS Parallel Benchmark BT as an example.
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