Comparing CM Fortran and Message-Passing Fortran Programming Modes on the CM-5

The Connection Machine CM-5 supports both SIMD and MIMD programming modes. The SIMD mode is simulated over the MIMD mode. This simulation is likely to lead to a loss of performance in SIMD programs. This paper describes the design and implementation of benchmarks which were used to bring out the diierence in speed between the two programming modes with CM Fortran and message-passing Fortran. Two kinds of benchmarks are discussed in this paper. The rst kind consists of synthetic benchmarks in which we measure time for basic arithmetic operations and communication time. The second kind comprises application benchmarks for which we have developed two typical applications in both programming modes using the same algorithm. The experimental results conclusively show that message-passing Fortran performs considerably better than CM Fortran.