Reading a Sparse matrix in CRS format from a function to be used in parallel linear solvers

[#DOMINIC DENVER JOHN CHANDAR#]

Hi,

   Thanks Hong and Matt. So looks like I don't have to call
MatSetValues() since I specify the row, column indices and the values
corresponding to it when I use  MatCreateMPIIJWithArrays()?

Cheers,
Dominic

-----Original Message-----
From: owner-petsc-users at mcs.anl.gov
[mailto:owner-petsc-users at mcs.anl.gov] On Behalf Of Hong Zhang
Sent: Wednesday, January 31, 2007 11:57 PM
To: petsc-users at mcs.anl.gov
Subject: Re: Reading a Sparse matrix in CRS format from a function to be
used in parallel linear solvers


Dominic,

You may use MatCreateMPIIJWithArrays() to achieve this.

Hong

On Wed, 31 Jan 2007, Matthew Knepley wrote:

> On 1/31/07, #DOMINIC DENVER JOHN CHANDAR# <DOMI0002 at ntu.edu.sg> wrote:
> >
> >  Hi,
> >
> >        I have a function which creates a sparse matrix following a 
> > certain eqn and returns a pointer to the row, column index and the 
> > value of a sparse matrix (CRS- form).
> > i   j   val
> > 1  1  1.0
> > 2  2  1.0
> > 2  3  -1.5..
> > so on...
> >
> >  The matrix *may not **have a definite pattern* like the one we see 
> > for tridiagonal or pentadiagonal matrices or the test cases (linear 
> > solvers) cited in the petsc documentation. Now, i would like to use 
> > the linear solvers in petsc to solve the system of equations. I do 
> > not want to write that sparse matrix into a file and read it into 
> > petsc since it may be huge.I would like to call that function from 
> > petsc and would return the pointer to i j and val and insert values 
> > of this sparse matrix using MatSetValues in parallel. How can I
achieve this ?
> >
>
> We do not have CRS format as it is not a very space efficient format. 
> Most of our formats are row-oriented. I suggest looking at the example

> for MatSetValues() and trying to rework the discretization function to

> directly call this. Most discretizations naturally generate row-by-row

> values or even blocks like FEM. Even totally nustructured stuff from 
> economics is row-by-row.
>
>   Thanks,
>
>     Matt
>
> Cheers,
> > Dominic
> >
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