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Memory requiremetns for the new MP2 gradient code

Roman Zubatyuk

Dear PC GAMESS developers/users.

I got insufficient memory error while performing large MP2 gradient calculation (Nocc=129, Ncore=52, Nvirt=981, distributed over 24 nodes each having 1GB of RAM). There are four options for the code those 'seriously affect amount of memory required': MXI, MXPQ, RSIZE1 and RSIZE2. Regarding this I have two questions:

1. If I'll halve MXI (or MXPQ), integral half-transformation (first or second) will be performed in two passes and thus approximately twice less memory will be needed. Am I right? Should I also change RSIZE1 (or  RSIZE2)?

2. Is there a formula to estimate memory requirement for various steps of MP2 calculation? Or the only solution is to perform check run? Should I run it in parallel, or serial check run will be sufficient?

Thanks in advance.
 Roman Zubatyuk

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