Petsc questions

[Barry Smith]

    Check AO functions. They renumber between two different orderings.

But, if your code already puts everything in the new numbering, you can
just use PETSc with that new numbering and leave your ordering code
as it is.

    Barry

On Aug 14, 2008, at 9:37 AM, Nguyen, Hung V ERDC-ITL-MS wrote:

>
> Hello All,
>
> I am new to PETSC. I have following questions about PETSC:
>
> 1. Do PETSC functions help to estimate/calculate a matrix condition  
> number?
> If yes, can I get the info how to do it?
>
> 2. A question about renumbering nodes: our CFD code uses ParMetis to  
> compute
> the original partitioning of the mesh.  The global nodes are  
> renumbered
> consecutively within each Parmetis partition as npetsc which is a  
> mapping
> vector from the original global node numbering to the new numbering,  
> see
> below as a test code. My question is whether PETSC function helps to  
> renumber
> from ParMetis partition to PETSC partition or not?
>
> Thank for your help.
>
> Regards,
>
> -Hung
> -- code:
> !         Read the data.
>
>      fname = 'petsc.dat'
>      call parnam (fname)
>      open (2, file = fname, status = 'old')
>
> !         No. global nodes, local nodes, owned nodes,
> !         compressed columns, PEs.
>
>      read (2, '(5i10)') ng, nloc, nown, ncol, npes
>
>      if (noproc .ne. npes) then
>        if (myid .eq. 0) then
>          print*, 'Number of PEs from the data file does not match',
>     &      ' the number from the run command.'
>        end if
>        call PetscFinalize (ierr)
>        stop
>      end if
>
> !         Local node array containing global node numbers.
>
>      allocate (nglobal(nloc))
>
>      read (2, '(8i10)') nglobal
>
> !         Find petsc numbering scheme.
>
>      allocate (nown_all(noproc))
>      allocate (idisp(noproc))
>      allocate (npetsc(nloc))
>      allocate (nodes1(ng))
>      allocate (nodes2(ng))
>
>      call MPI_ALLGATHER (nown, 1, MPI_INTEGER, nown_all, 1,
>     &  MPI_INTEGER, PETSC_COMM_WORLD, ierr)
>
>      idisp(1) = 0
>      do i = 2, noproc
>        idisp(i) = idisp(i - 1) + nown_all(i - 1)
>      end do
>
>      call MPI_ALLGATHERV (nglobal, nown, MPI_INTEGER, nodes1,
>     &   nown_all, idisp, MPI_INTEGER, PETSC_COMM_WORLD, ierr)
>
>      do i = 1, ng
>        ii = nodes1(i)
>        nodes2(ii) = i
>      end do
>
> !         Process the local nodes for their petsc numbers.
>
>      do i = 1, nloc
>        ii = nglobal(i)
>        npetsc(i) = nodes2(ii)
>      end do
>
>