Performance Considerations
One of the appeal of PC GAMESS is that you are likely to achieve very high performance on modern PC hardware with the right set of keywords. The performance of various parts can be further tuned by picking an algorithm best suited for a given problem size and computer hardware. There are lots of tuning options but some common suggestions are:
- Before performing a large calculation, perform a check run by specifying exetyp=check in the $contrl group and look for the suggestions the program offers.
- When performing not too large (less than ZZZ basis) SCF calculations, stay with the default conventional code. It is typically faster than the direct code, which can be requested by scfdir=1
- When performing MP2 calculations with small molecules (less than XXX basis functions), stay with the default conventional method ($mp2 method=2 $end).
- When performing MP2 calculations with large molecules (more than XXX basis functions), switch to the new direct method ($mp2 method=1 $end)