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Performance of CASSCF(15,15)...

Pavlo Solntsev

Dear Alex.

I am doing SA-CASSCF. Based on preliminary calculations (DFT,CIS-NO, MCSCF) and NBO analysis i realized that i have to use 15e15o active space at least for now to check the contribution of the orbitals into the MCSCF solution. My ground state is doublet. And as i expected there is a second excited doublet and quartet very close to my ground state. Therefore, i am doing SA-CASSCF (aldet) over two doublets and one quartet. I use 16 CPUs for this job. Unfortunately, this job is to large to allocate the amount of memory withing my CPU# window. I need ~550 MW. I found that MAXV variable in $det may reduce an amount of memory by cost of calculation time. In my case only MAXV=1 provides appropriate amount of memory, but job running so slowly. There are some variables in $det that can also affect amount of memory. I believe they are NHGSS, NSTGSS, MXXPAN and BLKSIZ.
I am interesting in three states but use 8 states with appropriate wstate(1) variable.
Based on the description NHGSS and BLKSIZ are suitable for a modification. Can you please advise me what is the best strategy here to overcome the memory problem? I also did a runtyp=check with distci=32 and it looks like it solves the memory problem for MAXV=4. I will try to get more CPUs but I am wondering, is it worth to spend time and play with 16 CPUs and settings or the best strategy is to switch to a larger number of processors.


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