[petsc-users] Quick question about ISCreateGeneral

[Sajid Ali]

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 ?

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
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