[petsc-users] VecScatter from slice of global vector to sequential vector + AO errors

[Randall Mackie]

I am trying to create a VecScatter that will scatter all the values from a
horizontal slice of a 3D DMDA global vector (with dof=3) to a sequential
vector on every processor. So far I have been unsuccessful, most likely
because I don't completely understand how to get the appropriate IS to do
this. I believe that you need to create a sequential IS on every processor
that has the PETSc global number for the appropriate values I want to
scatter. What I most recently tried was the following code which takes the
values at level k:

  DM          :: da3
  Vec         :: daSlice, daVec
  PetscInt    :: i, j, k, ierr, nis, istart, istep
  IS          :: from, to
  AO          :: ntog
  VecScatter  :: vscat
  PetscInt, allocatable :: indices(:)

  ! Get the AO context for this DM
  call DMDAGetAO(da3,ntog,ierr)

  ! Create indices for scatter from global vector
  allocate (indices(3*nx*ny))
  istart=(k-1)*nx*ny*3
  nis=nx*ny*3
  do i=1,nis
    indices(i)=istart+i-1
  end do

  ! Convert the indices from natural ordering to PETSc ordering
  call AOApplicationToPetsc(ntog,nis,indices,ierr)

  call
ISCreateGeneral(PETSC_COMM_SELF,nis,indices,PETSC_COPY_VALUES,from,ierr)

  ! Get the index set that specifies elements to scatter to sequential
vector
  istep=1
  istart=0
  nis=3*nx*ny
  call ISCreateStride(PETSC_COMM_SELF,nis,istart,istep,to,ierr)

  ! Create the Vector Scatter to get the values to every processor
  call VecScatterCreate(daVec,from,daSlice,to,vscat,ierr)

  ! Release memory
  deallocate (indices)
  call AODestroy(ntog,ierr)
  call ISDestroy(from,ierr)
  call ISDestroy(to,ierr)


This code is throwing errors as follows

[2]PETSC ERROR: --------------------- Error Message
------------------------------------
[2]PETSC ERROR: Invalid argument!
[2]PETSC ERROR: Wrong type of object: Parameter # 1!
[2]PETSC ERROR:
------------------------------------------------------------------------
[2]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[2]PETSC ERROR: See docs/changes/index.html for recent updates.
[2]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[2]PETSC ERROR: See docs/index.html for manual pages.
[2]PETSC ERROR:
------------------------------------------------------------------------
[2]PETSC ERROR: Libraries linked from
/home/rmackie/PETSc/petsc-3.4.2/linux-gfortran-debug/lib
[2]PETSC ERROR: Configure run at Thu Sep 19 15:08:47 2013
[2]PETSC ERROR: Configure options --with-scalar-type=complex
--with-debugging=1 --with-fortran=1 --download-mpich=1
[2]PETSC ERROR:
------------------------------------------------------------------------
[2]PETSC ERROR: AOApplicationToPetsc() line 261 in
/home/rmackie/PETSc/petsc-3.4.2/src/vec/is/ao/interface/ao.c
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Invalid argument!
[0]PETSC ERROR: Wrong type of object: Parameter # 1!
[0]PETSC ERROR:
------------------------------------------------------------------------
[1]PETSC ERROR: --------------------- Error Message
------------------------------------
[1]PETSC ERROR: Invalid argument!
[1]PETSC ERROR: Wrong type of object: Parameter # 1!
[1]PETSC ERROR:
------------------------------------------------------------------------
[1]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[1]PETSC ERROR: See docs/changes/index.html for recent updates.
[1]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[1]PETSC ERROR: See docs/index.html for manual pages.
[1]PETSC ERROR:
------------------------------------------------------------------------
[1]PETSC ERROR: Libraries linked from
/home/rmackie/PETSc/petsc-3.4.2/linux-gfortran-debug/lib
[1]PETSC ERROR: Configure run at Thu Sep 19 15:08:47 2013
[1]PETSC ERROR: Configure options --with-scalar-type=complex
--with-debugging=1 --with-fortran=1 --download-mpich=1
[1]PETSC ERROR:
------------------------------------------------------------------------
[1]PETSC ERROR: AOApplicationToPetsc() line 261 in
/home/rmackie/PETSc/petsc-3.4.2/src/vec/is/ao/interface/ao.c
[0]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR: -----------------------------------

etc.


First, I don't see where my error is that is causing these problems, but
second, is there a better way to create this vector scatter without having
to use an AO? I suspect there is,  but so far I have been unable to figure
out how to create the correct IS.

Thanks very much,

Randy
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