[petsc-users] DIstribute a global vector

[Dominik Szczerba]

I have my parallel layout and I can easily gather my MPI Vec's
components into one sequential Vec on root process using
VecScatterCreateToZero. Works perfectly.

But now I want the opposite: "VecScatterCreateFromZero". There is no
such function, but it well depicts my intention: I know my parallel
layout, I have a sequential Vec on root process that I want to be
partitioned and distributed to all processes. After studying all
VecScatter* functions I remain unsure how to best accomplish it, e.g.
VecScatterCreateToAll sounds promising but seems to scatter the whole
vector while I need to scatter only relevant processor chunks. I think
along these lines:

// arrayGlobal is a sequential vector on root with known size and in
application ordering.
// arrayLocal is a MPI vector with known global and local sizes.
IS ix;
// Fill ix on each process with global ID's this process owns
ierr = VecScatterCreate(arrayGlobal, ix, arrayLocal, PETSC_NULL, &scatter);

Is this right or is there a better/more elegant way?

Many thanks for any hints,
Dominik