Hi,

Is there an easy way to gather all values of an IS across all processes in a communicator while removing duplicates?

Basically, I want to go from
[0] Number of indices in set 2
[0] 0 1
[0] 1 2
[1] Number of indices in set 2
[1] 0 2
[1] 1 3

to
[0] Number of indices in set 3
[0] 0 1
[0] 1 2
[0] 2 3
[1] Number of indices in set 3
[1] 0 1
[1] 1 2
[1] 2 3

The way I do it right now is
ierr = ISGetTotalIndices(csIS,&labels);CHKERRQ(ierr);
ierr = ISGetSize(csIS,&num_cs_global);CHKERRQ(ierr);

I would violate PETSc semantics here since you are going to destroy csIS anyway:

PetscSortRemoveDupsInt(&num_cs_global, labels);

ISCreateGeneral(comm, num_cs_global, labels, PETSC_COPY_VALUES, &csIS_global);

ierr = ISRestoreTotalIndices(csIS,&labels);CHKERRQ(ierr);

Matt

Blaise
--
Department of Mathematics and Center for Computation & Technology
Louisiana State University, Baton Rouge, LA 70803, USA
Tel. +1 (225) 578 1612, Fax +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin