Exploiting autotasking on a CRAY Y-MP: An improved software interface to multitasking

Abstract

Modern supercomputers like the CRAY Y-MP achieve their high computing speed by using both vector and parallel hardware. Autotasking, the new multitasking interface on CRAY machines, supports an approach to parallelize FORTRAN programs automatically. The autotasking concept provides a user-friendly interface which can be used efficiently for fine-grain parallelism and removes some of the limitations which have restricted the usage of multitasking in the past. This paper gives a short introduction into the CRAy Y-MP system architecture and the autotasking concept. The application of autotasking to a program simulating the Czochralski bulk flow is presented. It can be shown that after some code modifications a speedup of nearly 6.5 on a CRAY Y-MP8/832 can be achieved, leading to a performance of about 1200 Mflops.