[petsc-users] Questions about DMDA Local and Global vectors

Anush Krishnan anush at bu.edu
Mon Nov 4 11:09:18 CST 2013


I have some questions about the differences between distributed local and
global vectors that are created using the same DM.

   1. I used a local vector for 'x' in the KSPSolve function, and I got a
   size mismatch error (due to extra ghost points on the local vector). So I
   had to use a global vector to perform the linear solve, and then later copy
   the values to a local vector to be able to perform finite-difference
   stencil-type operations. This doubles my memory usage. Is there a way to
   use this without the extra storage?
   2. When I use VecView to print the vectors to file, the global vector
   gets printed in full, but only the local values on process 0 are printed
   for a local vector.
   3. Should I assume that I always pass only global vectors to PETSc
   functions, and use local vectors only when I perform the stencil operations?

Thank you,
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