[petsc-users] Quick question about ISCreateGeneral

Matthew Knepley knepley at gmail.com
Tue Apr 30 16:04:00 CDT 2019

On Tue, Apr 30, 2019 at 12:42 PM Sajid Ali via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hi PETSc Developers,
> I see that in the examples for ISCreateGeneral, the index sets are created
> by copying values from int arrays (which were created by PetscMalloc1 which
> is not collective).
> If I the ISCreateGeneral is called with PETSC_COMM_WORLD and the int
> arrays on each rank are independently created, does the index set created
> concatenate all the int-arrays into one ? If not, what needs to be done to
> get such an index set ?

It does not sound scalable, but you can use


> PS: For context, I want to write a fftshift convenience function (like
> numpy, MATLAB) but for large distributed vectors. I thought that I could do
> this with VecScatter and two index sets, one shifted and one un-shifted.
> Thank You,
> Sajid Ali
> Applied Physics
> Northwestern University

What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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