A MASSIVELY-PARALLEL MULTIREFERENCE CONFIGURATION-INTERACTION PROGRAM- THE PARALLEL COLUMBUS PROGRAM

A massively parallel version of the configuration interaction (CI) sec tion of the COLUMBUS multireference singles and doubles CI (MRCISD) pr ogram system is described. In an extension of our previous paralleliza tion work, which was based on message passing, the global. array (GA) toolkit has now been used. For each process, these tools permit asynch ronous and efficient access to logical blocks of 1- and 2-dimensional (2-D) arrays physically distributed over the memory of all processors. The GAs are available on most of the major parallel computer systems enabling very convenient portability of our parallel program code. To demonstrate the features of the parallel COLUMBUS CI code, benchmark c alculations on selected MRCI and SRCI test cases are reported for the GRAY T3D, Intel Paragon, and IBM SP2. Excellent scaling with the numbe r of processors up to 256 processors (GRAY T3D) was observed. The CI s ection of a 19 million configuration MRCISD calculation was carried ou t within 20 min wall clock time on 256 processors of a GRAY T3D. Compu tations with 38 million configurations were performed recently; calcul ations up to about 100 million configurations seem possible within the near future. (C) 1997 by John Wiley & Sons, Inc.