Re: CSR Sparse Matrix Query

["Dr. Timothy Stitt" <timothy.stitt@xxxxxxxx>]

Hi everyone...again.

Thanks to the great support I have now got my solver working (in 
Fortran) albeit in a sequential non-distributed version. My problem is 
that I planned to substitute the call to MatCreateSeqAIJWithArrays() 
with a call to MatCreateMPIAIJWithArrays() (along with suitable 
modification to the arguments) to obtain a parallel version.

Anyhow, I have come upon a few problems() unfortunately. Firstly here 
are the code segments I am trying to update (my sparse matrix is square 
with global dimensions [rows,rows], size is returned by MPI_COMM_SIZE()):

---------------------------------------------------------------------------------------------------------------
call MatCreateSeqAIJWithArrays(PETSC_COMM_WORLD,rows,rows,&
       csrRowPointers,csrColumnIndices,csrElements,A,ierr)
----------------------------------------------------------------------------------------------------------------

TO

---------------------------------------------------------------------------------------------------------------
call 
MatCreateMPIAIJWithArrays(PETSC_COMM_WORLD,rows/size,rows/size,rows,rows,&
       csrRowPointers,csrColumnIndices,csrElements,A,ierr)
----------------------------------------------------------------------------------------------------------------

1. Firstly, when I compile the code I keep getting:

solver.o(.text+0x202): In function `MAIN__':
: undefined reference to `matcreatempiaijwitharrays_'

2. Do the arguments to the routine look correct ? I would prefer for 
PETSc to determine as many of the arguments as possible but I wasn't 
sure which ones to supply explicitly or allow PETSc to infer implicitly.

3. When constructing the operator matrix is it o.k. to build it only on 
node with rank 0 or does it have to be duplicated across all nodes 
before the call to the MatCreateMPIxxxxx() routine? The matrix is very 
large and hence wouldn't be suitable for replication.

I hope this is the last of my worries. Thanks again for your support and 
patience.

Regards,

Tim.



Satish Balay wrote:
> On Mon, 23 Apr 2007, Satish Balay wrote:
>
>   
> > On Mon, 23 Apr 2007, Dr. Timothy Stitt wrote:
> >
> >     
> > > I am using Fortran. Do I have to perform some operation to switch
> > > from column-major to row-major representation before calling the
> > > MatCreateSeqAIJWithArrays routine? 
> > >       
> > MatCreateSeqAIJWithArrays expects a 1d array for the values [and
> > rows,column indicies as well] - so this issue of row-major vs
> > column-major does not exist.
> >     
>
> However the CSR format which is used for the input, is equivalent to a
> row-major ordering.. i.e for the following matrix:
>
> 1 0 0
> 2 0 3
> 0 4 5
>
> The call expects the following
>
> i =  {0,1,3,5}  [size = nrow+1  = 3+1]
> j =  {0,0,2,1,2}  [size = nz = 5]
> v =  {1,2,3,4,5}  [size = nz = 5]
>
> Satish
>
>   


--
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)