ELSEVIER Parallel Computing 20 (1994) 363-373 PARALLEL COMPUTING Practical aspects and experiences A comparative study of the use of the data-parallel approach for compressible flow calculations M.L. Sawley a, C.M. Bergman b a Institut de Machines Hydrauliques et de M~canique des FluMes, Ecole Polytechnique F~ddralede Lausanne (EPFL), CH-1015 Lausanne, Switzerland b Centerfor Computational Mathematics and Mechanics, Kungliga Tekniska H6gskolan (KTH), S-100 44 Stockholm, Sweden (Received 8 February 1993; revised 24 May 1993) Abstract The results are presented of an investigation into the use of the data-parallel program- ming approach on four different massively-parallel computers: the MasPar MP-1 and MP-2 and the Thinking Machines CM-200 and CM-5. A code to calculate inviscid compressible flow, originally written in FORTRAN 77 for a traditional vector computer, has been re-written entirely in Fortran 90 to take advantage of the compilers available on the massively-parallel computers. It is shown that the discretization of the governing equations on a regular mesh is well adapted to data parallelism. For a typical test problem of supersonic flow through a ramped duct, computational speeds have been achieved using these massively-parallel computers that are superior to those obtained using a single processor of a Cray Y-MP. In addition, this study has enabled the question of code portability between the different computers to be assessed. Key words: Computational fluid dynamics; Euler equations; Data-parallel programming; Portability; Performance results 1. Introduction The field of Computational Fluid Dynamics (CFD), which deals with the numerical simulation of fluid flows, has become increasingly important over recent years due to its application to a large number of engineering problems. Most applications of CFD are based on the resolution of a set of partial differential equations (e.g. the Navier-Stokes equations, or a simplified set of equations such 0167-8191/94/$07.00 9 1994 Elsevier Science B.V. All rights reserved SSD! 0167-8191(93)E0085-A