[molpro-user] VCI - insufficient memory available

[Dinu, Dennis Florian]

Dear Molpro-Community,

first of all the SURF/VSCF/VCI programs in molpro perform really nice, the majority of the anharmonic vibrational calculations were unproblematic and all in all the experience was very user-friendly. But now that I switched to a bigger System (C2H4O3), I run into a memory problem, which I cannot solve from the rather brief error output.

Setup: precompiled Molpro 2015.1 / Intel Xeon CPU E5-2643 v3 / 12 cores / 256 GB RAM
The error message:
--------------------------------------------------------------------------------------------------
PROGRAM * VCI (Vibrational configuration interaction)   Authors: G. Rauhut 2004, M. Neff 2009, D. Oschetzki 2013

Reading potential from record        5600.2
Reading wave function from record    5750.2

Results of VCI calculation:

Number of configurations:    A`      1259812   ( S:       84  D:     3528  T:    91210  Q:  1164989 )
                                             A``     1023169   ( S:       21  D:     1722  T:    61740  Q:   959686 )

Fundamentals

Mode         E(abs)      VCISDTQ      IR Intens     Leading term        Type    Dim.      CPU tot.       CPU #
    0        14548.94         0.00                                   0.9507             J         5721       11616.6     11616.6
insufficient memory available - require               26270376  have
             25383256
the request was for real words
--------------------------------------------------------------------------------------------------

The calculation was started with 512 Megawords per CPU, so the error message, saying that there are just about 25 Megawords available is rather strange for me. I already tried much less (100 Megawords), and much more (1024 Megawords) memory allocation per CPU, but with the same error message.

There are some posts in the mailing-lists concerning this, most of then within electronic structure theory. Here some examples:
CASSCF calculation: http://www.molpro.net/pipermail/molpro-user/2005-June/001380.html
CCSD(T) calculation: http://www.molpro.net/pipermail/molpro-user/2009-June/003122.html
UCCSD(T)-F12 calculation: http://www.molpro.net/pipermail/molpro-user/2011-April/004320.html
and much more..

The main answers that i found:
1) Increase the memory until the calculation works.
Question: For the CC programs, molpro suggests the amount of memory it needs. Is there a similar output for the VCI progams?

2) Adjust size of the shmmax kernel parameter in /proc/sys/kernel/shmmax
Question: For the MPI-2 version of molpro, this parameter should not be of interest.. is that right?

Are there any other suggetions and answers to that problem?

PS: On our large-memory nodes, we have no SWAP. Could that be a problem for the molpro system?

greets

Dennis Dinu
Institute of Theoretical Chemistry
University of Innsbruck



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