The authors present the results of an architectural comparison of SIMD (single-instruction multiple-data) massive parallelism, as implemented in the Thinking Machines Corp. CM-2, and vector or concurrent-vector processing, as implemented in the Cray Research Inc., Y-MP/8. The comparison is based primarily upon three application codes taken from the LANL (Los Alamos National Laboratory) CM-2 workload. Tests were run by porting CM Fortran codes to the Y-MP, so that nearly the same level of optimization was obtained on both machines. The results for fully configured systems, using measured data rather than scaled data from smaller configurations, show that the Y-MP/8 is faster than the 64 k CM-2 for all three codes. A simple model that accounts for the relative characteristic computational speeds of the two machines, and reduction in overall CM-2 performance due to communication or SIMD conditional execution, accurately predicts the performance of two of the three codes. The authors show the similarity of the CM-2 and Y-MP programming models and comment on selected future massively parallel processor designs.>

Delays caused by memory access conjiicts were measured for vector operations on the CRAY Y-MP and CRAY X-MP, and on two versions of the CRAY-2 with static and dynamic memory.The delays were measured as jimctions of vector length and the number of active processors.The observed delays were lowest for memory access operations with stride one.Considerably higher delays were observed for mixed strides or random access.For access operations with mixed strides, measurements indicate that memory access was slowed down by a factor of up to 1.7 for the 8-processor CRAY Y-MP.For the 4processor machines, the factors were 3.1 for the CRAY X-MP, 4.4 for the CRAY-2 with dynamic memory, and 2.5 for the CRAY-2 with static memory.The results are compared with a queueing model of memory bank conjiicts.A model of vector performance with vector loop unrolling is presented as a special case of a previously published model.

The performance of two second-generation supercomputers, the NEC SX-3 and the Fujitsu VP2600, is analyzed using the Standard Los Alamos Benchmark Set, the Mendez Fluid Dynamics Codes, and some highly vectorizable production-type codes from Los Alamos.For comparison, data are also given for a single processor of the CRAY Y-MP8/264.Factors affecting performance such as memory bandwidth, vector register organization, and the effects of multiple vector pipelines are examined.On a highly vectorizable code that can take advantage of multiple vector pipes, the SX-3 and VP2600 are faster than the single CRAY Y-MP processor by factors of seven to eight.

The authors report the performance of the 6000-series computers as measured using a set of portable, standard-Fortran, computationally intensive benchmark codes that represent the scientific workload at the Los Alamos National Laboratory. On all but three of the benchmark codes, the 40-ns RISC (reduced instruction set computer) system was able to perform as well as a single Convex C-240 processor, a vector processor that also has a 40-ns clock cycle, and, on these same codes, it performed as well as the FPS-500, a vector processor with a 30-ns clock cycle.>

The serial and parallel performance of the Cray-2 is analyzed using the standard Los Alamos benchmark set plus codes adopted for parallel processing. For comparison, architectural and performance data are given for the Cray-X-MP/416. Factors affecting performance, such as memory bandwidth, size and access speed of memory, and software exploitation of hardware, are examined. The parallel-processing environments of both machines are evaluated, and speedup measurements for the parallel codes are given.>

article A close look at vector performance of register-to-register vector computers and a new model Share on Authors: Ingrid Y. Bucher Los Alamos National Laboratory, Los Alamos, New Mexico Los Alamos National Laboratory, Los Alamos, New MexicoView Profile , Margaret L. Simmons Los Alamos National Laboratory, Los Alamos, New Mexico Los Alamos National Laboratory, Los Alamos, New MexicoView Profile Authors Info & Claims ACM SIGMETRICS Performance Evaluation ReviewVolume 15Issue 1May 1987 pp 39–45https://doi.org/10.1145/29904.29911Online:01 May 1987Publication History 11citation218DownloadsMetricsTotal Citations11Total Downloads218Last 12 Months5Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access