GAMESS

Nick Nystrom

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Scientific Significance:

GAMESS (General Atomic and Molecular Electronic Structure System) is a quantum chemistry code currently being developed at Iowa State University. Its particular strength is the ability to efficiently perform MCSCF calculations (Multi-Configuration Self-Consistent Field) and it is superior to other widely used programs for that purpose.

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Numerical Approach and Performance:

GAMESS is written in standard Fortran 77 and runs on a variety of platforms. The program exhibits poor performance on Cray vector hardware. However, as distributed by the author, it provides support for message-passing parallelism. This is accomplished through calls to the TCGMSG message passing library. Because most computation is done in parallel regions and these regions are scattered through the code, GAMESS is better suited to a standalone T3D implementation than it is to the heterogeneous C90/T3D platform. The TCGMSG library was replaced by a set of wrappers to call the appropriate PVM routines. The code would not run under the T3D emulator, so it was necessary to do development work on the PSC workstation cluster. Once the T3D hardware arrived and the software stabilized, GAMESS ran. However, because of early memory limitations on the T3D, it was limited to direct (in memory) calculations with about 200 basis functions. This is marginally enough to handle interesting problems. Since the upgrade of memory to 8MW/PE it has become possible to run problems with up to about 900 basis functions.

Benchmark 1 = SiC2H6 RHF/6-31G* 61 basis functions
Benchmark 4 = SiC3H8 RHF/6-31G* 80 basis functions
Benchmark 8 = SnC5H6 GVB/3-21G* 96 basis functions
Benchmark 9 = C6H8 UHF/DH(d,p) 130 basis functions
Benchmark 10 = P2H4+ ROHF+gr./DH(d) 56 basis functions
Benchmark 12 = SbC4H4No2 RHF+gr/3-21G* 110 basis functions
Phosphinoaluminate = (CH3)2 AIP-2 RHF+gr./6-311G(d,p) 169 basis functions

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