[DFTB-Plus-User] Max Number of Atoms

[Benjamin Hourahine]

Hello Marcelo,

Have you ruled out the stack size issue with ifort, which I also mailed
you about?

The probable reason for your discrepancy in estimating the memory is that
both the Hamiltonian and overlap matrices have to be held in memory
when using the LAPACK generalized eigensolvers. Incidentally, are you
sure that you aren't using the divide and conquer eigensolver?

Cheers

Ben

    Dr. B. Hourahine, Department of Physics, SUPA, University of Strathclyde,
      John Anderson Building, 107 Rottenrow, Glasgow G4 0NG, United Kingdom
    Ph +44 141 548 2325 FAX +44 141 552 2891 benjamin.hourahine at strath.ac.uk

The University of Strathclyde is a Scottish registered charitable body, number SC015263




-----Original Message-----
From: dftb-plus-user-bounces at dftb-plus.info on behalf of Marcelo Zimmer
Sent: Tue 07/10/2008 15:10
To: User list for DFTB+ related questions
Subject: Re: [DFTB-Plus-User] Max Number of Atoms
 
Dr. B. Hourahine,

Thank you for prompt answer. Actually, by "unexpected error" I meant: the
job stoped without any error message. For this, I was wondering if the
problem was caused by lack of memory or any limitation related to vector
size allocation, which would limit the maximum number of atoms independent
on hardware availability. Anyway, my calculations rely on the first case
you've mentioned and I'm convinced the problem is lack of memory, although
my expectations were that my calculations would require ~10Gb.

Best regards,

Marcelo Zimmer

--
===================================================
                              Marcelo Zimmer S. Flores
                                (PhD Physics Student)

Address:
      Universidade Estadual de Campinas - UNICAMP
      Instituto de Fisica Gleb Wataghin - IFGW
      Grupo de Solidos Organicos e Novos Materiais - GSONM
      Departamento de Fisica Aplicada (DFA) - Room 61
      Campinas - Sao Paulo - Brazil
      13083-970
      Caixa Postal: 6165
      zimmer at ifi.unicamp.br
===================================================

On Mon, Oct 6, 2008 at 19:26, Benjamin Hourahine <
benjamin.hourahine at strath.ac.uk> wrote:

> Hello Marcelo,
>
> I'll need some more information to give an accurate answer, but
> if I assume all of the atoms have an SP basis, you have SCC
> turned on, are using molecular boundary conditions (not periodic),
> no spin polarization, and the 'standard' or 'relatively robust'
> choice of eigensolvers then I'd estimate your memory requirements
> at about 17 Gb for that system.
>
> If you use the default eigensolver (divide and conqer) this would rise
> to a peak of about 28 Gb when it requires workspace. Similarly, changing
> any of the above calculational conditions could also modify the memory use.
>
> This suggests you are running out of memory. What exactly is the
> 'unexpected error'?
>
> Cheers
>
> Ben
>
>    Dr. B. Hourahine, Department of Physics, SUPA, University of
> Strathclyde,
>      John Anderson Building, 107 Rottenrow, Glasgow G4 0NG, United Kingdom
>    Ph +44 141 548 2325 FAX +44 141 552 2891
> benjamin.hourahine at strath.ac.uk
>
> The University of Strathclyde is a Scottish registered charitable body,
> number SC015263
>
>
>
>
> -----Original Message-----
> From: dftb-plus-user-bounces at dftb-plus.info on behalf of Marcelo Zimmer
> Sent: Mon 06/10/2008 19:47
> To: User list for DFTB+ related questions
> Subject: [DFTB-Plus-User] Max Number of Atoms
>
> Hello all DFTB+ users,
>
> I`d like to know what is the maximum number of atoms that DFTB+ can carry
> on
> calculation for a molecule. I`m trying to compute approx. 8,000 atoms and
> I`m having unexpected error during the first SCC cycle. I`m trying to run
> this job under 8 Intel(R) Xeon(R) CPU E5420 @ 2.50GHz with 16Gb of RAM.
>
> Thank you in advance,
>
> Marcelo Zimmer
>
> --
> ===================================================
>                               Marcelo Zimmer S. Flores
>                                 (PhD Physics Student)
>
> Address:
>       Universidade Estadual de Campinas - UNICAMP
>       Instituto de Fisica Gleb Wataghin - IFGW
>       Grupo de Solidos Organicos e Novos Materiais - GSONM
>       Departamento de Fisica Aplicada (DFA) - Room 61
>       Campinas - Sao Paulo - Brazil
>       13083-970
>       Caixa Postal: 6165
>       zimmer at ifi.unicamp.br
> ===================================================
>
>
> _______________________________________________
> DFTB-Plus-User mailing list
> DFTB-Plus-User at dftb-plus.info
> http://www.dftb-plus.info/mailman/listinfo/dftb-plus-user
>



-- 
===================================================
                               Marcelo Zimmer S. Flores
                                 (PhD Physics Student)

Address:
       Universidade Estadual de Campinas - UNICAMP
       Instituto de Fisica Gleb Wataghin - IFGW
       Grupo de Solidos Organicos e Novos Materiais - GSONM
       Departamento de Fisica Aplicada (DFA) - Room 61
       Campinas - Sao Paulo - Brazil
       13083-970
       Caixa Postal: 6165
       zimmer at ifi.unicamp.br
===================================================