Exploitation of Data in Memory in the FIDAP Code on the IBM ES/3090

Abstract

The IBM ESA/370 architecture incorporates unique features that are of benefit in numerical intensive applications. One of these features, as implemented in the MVS/ESA operating system, is the hiperspace, an extension to the addressing scheme available on the base System/370-XA, that allows indirect access to Expanded Storage. Access to hiperspaces has been implemented through usage of the Data Window Services library of MVS/ESA.

The present paper discusses a hiperspace exploitation for the IBM 3090 of the FIDAP (*) Finite Element code, that analyses 2-D and 3-D incompressible viscous fluid flow.

In FIDAP, if the storage available is not sufficient for solving the problem in-core, the solver splits the system into blocks that are put into a FORTRAN logical unit. For very complex geometries, the limit of two gigabytes virtual storage in IBM System/370-XA can well be surpassed. In that case, heavy I/O activity can reduce performance of the solver. MVS/ESA permits fast access to hiperspaces through windows in virtual storage; FIDAP takes advantage of that feature by transforming access to the spill unit into access to a hiperspace, thus gaining a reduction of up to three in elapsed time.

The purpose of the work was to demonstrate the capability of the standard IBM VS FORTRAN compiler and MVS/ESA operating system to optimally compile and execute an industrial code like FIDAP on a supercomputer exploiting its storage hierarchy, and particularly virtual and Expanded Storage, with small intervention on the programmer’s part.

The paper also presents performances and results concerning an industrial test case involving thermocapillary convection.

Article Note

FIDAP is a registered trademark of Fluid Dynamics International.