External software help

[Satish Balay]

On Mon, 12 Feb 2007, Ben Tay wrote:

> Hi,
> 
> I'm trying to experiment with using external solvers. I have some questions:
> 
> 1. Is there any difference in speed with calling the external software from
> PETSc or directly using them?

There is minor conversion overhead when you use them from PETSc.

> 
> 2. I tried to install MUMPS using  --download-mumps. I was prompted to
> include --with-scalapack. After changing, I was again prompted to include
> --with-blacs. I changed and again I was told the need for
> --with-blacs-dir=<directory>. I thought I'm supposed to specify where to
> install blacs and entered a directory. But it seems that I need to specify
> the location of where blacs is. But I do not have it. So how do I solve
> that?

Mumps requires blacs & scalapack. So use:
--download-blacs=1 --download-scalapack=1 --download-mumps=1

> 
> 3. I installed some other external packages. I wanted to test their speed at
> solving equations. In the manual, I was told to use the runtime option
> -mat_type <mattype> -ksp_type preonly -pc_type <pctype> and also -help to
> get help msg. However when I tried to issue ./a.out -mat_type superlu
> -ksp_type preonly -pc_type lu, nothing happened. How should the command be
> issued? I tried to get help by running ./a.out -h what appears isn't what I
> want.

Did you install PETSc with superlu_dist? If so use '-mat_type superlu_dist'

[Note: superlu & superlu_dist are different packages - the first one
is sequential - the second one is parallel]

Satish

> 
> Thank you very much. Regards.
>