External software help

[Ben Tay]

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?

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?

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.

Thank you very much. Regards.
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