[petsc-users] MatShellGetContext in Fortran

Timothée Nicolas timothee.nicolas at gmail.com
Wed Oct 7 13:19:33 CDT 2015

Hi all,

In the manual, it says, about MatShellSetContext and MatShellGetContext,
that in FORTRAN we cannot set a context other than integer or PetscObject.


In my understanding, it means that I would be allowed to do, say

PetscInt :: ione
call MatShellSetContext(A,ione,ierr)
call MatShellSetOperation(A,MATOP_MULT,MyMult,ierr)

in the routine where I define the matrix A, and then recover the integer in
the routine MyMult with

PetscInt :: intval
call MatShellGetContext(A,intval,ierr)

This would allow me to circumvent the interdiction to pass a real context,
by e.g. using a module at the beginning of MyMult, containing contexts and
discriminating which context to use with the value of the integer (I want
to use Multigrid, so I cannot have a different routine for each level
obviously). However, this approach did not work, the value in intval stays
undefined. How could I solve this ?


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