MatCreateMPIAIJ Pre-allocation Query

[Tim Stitt]

Actually my sparse matrix has >2^32 rows and columns hence the global row and 
column arguments need to be 64-bit.

On Sunday 17 June 2007 17:36, Barry Smith wrote:
>   If your problem is so big that you need integers that represent numbers
> more than about 2 billion then yes you will need to rebuild PETSc.
>
>   Barry
>
> You'll be the first PETSc user who solves a problem with more than
> 2 billion unknowns.
>
> On Sun, 17 Jun 2007, Tim Stitt wrote:
> > Thanks for that Matt...will check it out.
> >
> > Incidentally, I need to pass a 64-bit integer to MatCreateMPIAIJ. Do I
> > need to rebuild PETSc using a 64-bit integer option switch?
> >
> > Tim.
> >
> > On Sunday 17 June 2007 17:07, Matthew Knepley wrote:
> > > On 6/17/07, Tim Stitt <timothy.stitt at ichec.ie> wrote:
> > > > Hi All,
> > > >
> > > > Currently I am using MatCreateMPIAIJ to create a distributed sparse
> > > > matrix for use in my parallel sparse eigensolver. If I understand
> > > > things correctly, it is important to specify the correct
> > > > pre-allocation values for (o_nz,d_nz) or (o_nnz, d_nnz) respectively
> > > > to obtain optimum memory usage per node.
> > > >
> > > > For information my matrix redistribution routine generates each row
> > > > in the sparse matrix (associated with a given node) "on-the-fly" and
> > > > then uses MatSetValues to apply the elements.
> > > >
> > > > My question is: does anyone have a standard code template for the
> > > > calculating the d_nz or d_nnz values (along with o_nz or o_nnz
> > > > respectively) so that optimum pre-allocation is obtained? Is there a
> > > > simple way of determining if a given non-zero value in a row is part
> > > > of the diagonal or off-diagonal regions for a given distributed
> > > > topology?
> > > >
> > > > Any assistance gratefully received.
> > >
> > > Basically, you run through the construction algorithm once to calculate
> > > d_nnz and o_nnz, and then again to set values. You can see my code for
> > > doing it in preallocateOperator() in src/dm/mesh/mesh.c.
> > >
> > >    Matt
> > >
> > > > Thanks in advance,
> > > >
> > > > Tim.
> > > >
> > > > --
> > > > Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
> > > > HPC Application Consultant - ICHEC (www.ichec.ie)
> > > >
> > > > Dublin Institute for Advanced Studies
> > > > 5 Merrion Square - Dublin 2 - Ireland
> > > >
> > > > +353-1-6621333 (tel) / +353-1-6621477 (fax) / +353-874195427 (mobile)

-- 
Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
HPC Application Consultant - ICHEC (www.ichec.ie)

Dublin Institute for Advanced Studies
5 Merrion Square - Dublin 2 - Ireland

+353-1-6621333 (tel) / +353-1-6621477 (fax) / +353-874195427 (mobile)