> On May 19, 2018, at 11:42 AM, Praveen C <[email protected]> wrote:
>
> Thanks a lot.
>
>> On 19-May-2018, at 9:16 PM, Smith, Barry F. <[email protected]> wrote:
>>
>> Praveen,
>>
>> Ahh, we didn't have support for passing PETSC_NULL_MAT from Fortran for
>> this routine. I have added it in the branch
>> barry/fix-null-matrix-set-jacobian/maint which after testing will go into
>> the maint branch.
>>
>> Could you please try this branch and let us know if it resolves the
>> problem (or a new problem pops up)?
>>
>> Barry
>>
>> Unfortunately handling null objects from Fortran requires us to manually
>> tweak the Fortran interface functions and sometimes we forget or don't
>> realize they need fixing until someone reports a problem.
>
> I meanwhile passed a Mat object to TSSetRHSJacobian function. It seems that
> with -snes_mf and PCSHELL, my RHSJacobian is never invoked. Is this the
> correct behaviour ?
Yes, if you want your function to be called you need to use
-snes_mf_operator instead.
>
> In RHSJacobian, I am storing the current solution into my usercontext so that
> I can use it in my shell preconditioner
>
> subroutine RHSJacobian(ts, time, u, J, P, ctx, ierr)
>
> call VecCopy(u, ctx%p%v_u, ierr); CHKERRQ(ierr)
>
> end
>
> However, since my RHSJacobian is never invoked, I dont have access to the
> current solution needed in my ApplyPC. How can I access the current solution
> in my ApplyPC function ?
>
> Another issue I am facing is this. I attach my user context to the PC
>
> call TSGetSNES(ts, snes, ierr); CHKERRQ(ierr)
> call SNESGetKSP(snes, ksp, ierr); CHKERRQ(ierr)
> call KSPGetPC(ksp, pc, ierr); CHKERRQ(ierr)
> call PCSetType(pc, PCSHELL, ierr); CHKERRQ(ierr)
> call PCShellSetContext(pc, ctx, ierr); CHKERRQ(ierr)
> call PCShellSetApply(pc, ApplyPC, ierr); CHKERRQ(ierr)
>
> Inside my ApplyPC, I access ctx using
>
> subroutine ApplyPC(pc, x, y, ierr)
> use petscpc
> use mtsdata
> implicit none
> PC :: pc
> Vec :: x, y
> PetscErrorCode :: ierr
> ! Local variables
> type(tsdata) :: ctx
>
> call PCShellGetContext(pc, ctx, ierr); CHKERRQ(ierr)
>
> end
>
> But the ctx I get from above is not correct, since it does not have the data
> I stored in my original ctx.
This won't work. You need to use a pointer for the context not an entirely
new context argument. See
src/mat/examples/tutorials/ex6f.F90
for how to use derived data types and pointers with contexts in Fortran.
Barry
>
> I am rather clueless at this stage.
>
> Thanks for your help.
> Best regards
> praveen
