[petsc-users] Incrementing individual entries in vectors

[Derek Gaston]

I have a funky algorithm I'm working on... and in it I need to increment
individual entries in vectors in parallel and then finalize the vector,
summing to get the final value.  So, something like this:

If I have a vector "v" with 6 values in it (all starting at 0) spread
across two processors (so that the first 3 entries are on processor 0 and
the last three on processor 1).

On processor 0 I need to be able to do:

v[1]++;
v[2]++;
v[1]++;

Then on processor 1 I'd like to do:

v[0]++;
v[1]++'
v[5]++;
v[1]++;

Then, after finalizing the vector I'd like to end up with a vector that has
these values on processor 0:

v[0] -> 0
v[1] -> 4
v[2] -> 1

and on processor 1:

v[3] -> 0
v[4] -> 0
v[5] -> 1

Is there anything in PETSc that would help here??  I realize that I can
roll my own solution using arrays and MPI for this... but it would be handy
if I could do this with a PETSc Vec because the next step is to use
VecPointwiseDivide() to divide another vector by this funky one pointwise.
 Both of these vectors will have the same parallel distribution.  Also,
note that these vectors might be really large (like 300 million to 1
billion entries) so it would be really handy to have the automatic
parallelization of Vec...

Thanks for any help...

Derek
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20140123/31ac14b2/attachment.html>