A DISTRIBUTED-MEMORY IMPLEMENTATION OF THE MCHF ATOMIC-STRUCTURE PACKAGE

The MCHF (Multiconfiguration Hartree-Fock) atomic structure package co nsists of a series of programs that predict a range of atomic properti es and communicate information through files. Several of these have no w been modified for the distributed-memory environment. On the Intel i PSC/860 the restricted amount of memory and the lack of virtual memory required a redesign of the data organization with large arrays residi ng on disk. The data structures also had to be modified. To a large ex tent, data could be distributed among the nodes, but crucial to the pe rformance of the MCHF program was the global information that is neede d for an even distribution of the workload. This paper outlines the co mputational problems that must be solved in an atomic structure calcul ation and describes the strategies used to distribute both the data an d the workload on a distributed-memory system. Performance data are pr ovided for some benchmark calculations on the Intel iPSC/860.