Doubts concerning matrix reorderings!

Barry Smith bsmith at
Sun Mar 2 20:04:15 CST 2008

    The built in PETSc factorization routines are only sequential, so  
to do parallel LU (of Cholesky) factorization and solve
you need to build PETSc with one of the parallel solver packages: to  
do this you must config/ PETSc
with --download-spooles or --download-superlu_dist or --download-mumps  
--download-scalapack --download-blacs

    Now the people who write parallel factorization routines (for some  
reason I cannot understand) limit the reordering
that may be used to a few they have hardwired for their package. Thus  
the PCFactorSetMatOrdering() doesn't do
anything with the parallel factorization packages. If you look at the  
manual page for MATMPIAIJSPOOLES it shows
the possibilities, MATAIJMUMPS and MATSUPERLU_DIST

    Hope this clarifies things a bit,


On Mar 2, 2008, at 6:31 PM, Rafael Santos Coelho wrote:

> Hello, folks! (:
> My name is Rafael and in order to get started with PETSc, I began  
> writing a program which solves, in parallel, a simple fluid flow  
> linear problem. Now, I want to experiment more by trying some matrix  
> reordering schemes and observing the impact they might cause. So  
> after reading PETSc's documentation, I couldn't find good examples  
> to help me out. Say, for instance, I want to use RCM. How would it  
> be? Will a simple call to the PCFactorSetMatOrdering() function do  
> it? Or is there more? Just to remember you, it's a parallel code...
> Thanks in advance (:
> Rafael Santos Coelho

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