Question about MatSetValues

[Sh.M]

Thanks.

I will try that.

With best regards, Shaman Mahmoudi

----- Original Message ----- 
From: "Barry Smith" <bsmith at mcs.anl.gov>
To: <petsc-users at mcs.anl.gov>
Sent: Sunday, June 04, 2006 7:20 PM
Subject: Re: Question about MatSetValues


>
>    Write a SEQUENTIAL program that reads in the matrix and then
> saves it with MatView() to a binary file (can do a right hand side also)
> then use ksp/ksp/examples/tutorials/ex10.c which uses MatLoad() to solve
the
> system.
>
>    See for example src/mat/examples/tests/ex32.c for an example of
> sequential program for reading in ASCII matrix. Also ex34.c ex50.c also
ex78.c
>
>
>
>     Barry
>
>
> On Sun, 4 Jun 2006, Sh.M wrote:
>
> > Hi,
> >
> > When using the MatSetValues function with one CPU only, it will
cache/save
> > the values locally and then distribute them to the other processes with
> > MatAssemblyBegin/MatAssemblyEnd? Is this true? What happens with the
> > cached/saved values afterwards? Are they released? Is there a way to not
> > cache/save the data locally at all?
> >
> > I am asking these questions because right now speed is not of highest
> > priority, but memory is. And unfortunately in my case I do not generate
the
> > matrix by my own and instead read it from a file obtained from "real
world"
> > data samples.
> >
> > I have read/distributed the matrix in a couple of different ways; for
> > example CPU 0 reads the file, and then calls MatSetValues.. One other
way
> > has been that CPU 0 reads the file, sends the rows that belong to the
other
> > processes to the other processes and those processes call MatSetValues
by
> > their own on the received rows. And last one is that I have split the
file
> > into several smaller files and several processes reads their own file
and
> > call MatSetValues on the data they have read from their own file. To
make it
> > more convenient for me, the number of files have been maximum number of
> > processors that I have used in my simulations. So If maximum number of
> > processors is 64, then number of files is 64. And if 8 processors are
used,
> > then each processor reads 8 files etc.
> >
> > I dont believe any of the approaches I have used are elegant...
> >
> > What would you guys do if you had a file in CSR format, and you want to
read
> > it, distribute it and then solve it if memory usage is of highest
priority?
> >
> > With best regards, Shaman Mahmoudi
> >
> >
>