[petsc-users] matshell for spectral methods in fortran

[Luv Sharma]

Dear PETSc team,

I am working on a code which solves mechanical equilibrium using spectral methods.
I want to make use of the matshell to get the action J*v.

I have been able to successfully implement it using petsc4py. But having difficulties to get it working in a fortran code.
I am using petsc-3.7.6. 

Below is a stripped down version of the existing fortran code (module). Can you please help me in figuring out how the right way to do it a code with following structure?

!--------------------------------------------------------------------------------------------------
module spectral_mech_basic

 implicit none
 private
#include <petsc/finclude/petsc.h90>

! *PETSc data here*
 DM ..
 SNES ..
 ..
contains

!--------------------------------------------------------------------------------------------------
subroutine basicPETSc_init

 external :: &
   *petsc functions here*

! initialize solver specific parts of PETSc
 call SNESCreate(PETSC_COMM_WORLD,snes,ierr); CHKERRQ(ierr)
 call SNESSetOptionsPrefix(snes,'mech_',ierr);CHKERRQ(ierr)  
 call DMDACreate3d(PETSC_COMM_WORLD, &
        DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, &                                  
        DMDA_STENCIL_BOX, &                                                                         
        grid(1),grid(2),grid(3), &                                                          
        1 , 1, worldsize, &
        9, 0, &                                                                                    
        grid(1),grid(2),localK, &                                                             
        da,ierr)                                                                                  
 CHKERRQ(ierr)
 call SNESSetDM(snes,da,ierr); CHKERRQ(ierr)
 call DMCreateGlobalVector(da,solution_vec,ierr); CHKERRQ(ierr)                                    
 call DMDASNESSetFunctionLocal(da,INSERT_VALUES,BasicPETSC_formResidual,PETSC_NULL_OBJECT,ierr)    
 CHKERRQ(ierr) 
 call SNESSetDM(snes,da,ierr); CHKERRQ(ierr)                                                       
 call SNESGetKSP(snes,ksp,ierr); CHKERRQ(ierr)                                                    
 call KSPGetPC(ksp,pc,ierr); CHKERRQ(ierr)                                                          
 call PCSetType(pc,PCNONE,ierr); CHKERRQ(ierr)                                                     
 call SNESSetFromOptions(snes,ierr); CHKERRQ(ierr)                                                 

! init fields                 
 call DMDAVecGetArrayF90(da,solution_vec,F,ierr); CHKERRQ(ierr)                                    
 call DMDAVecRestoreArrayF90(da,solution_vec,F,ierr); CHKERRQ(ierr)                               

end subroutine basicPETSc_init
!--------------------------------------------------------------------------------------------------

type(tSolutionState) function &
  basicPETSc_solution(incInfoIn,timeinc,timeinc_old,stress_BC,rotation_BC)
 implicit none
! PETSc Data
 PetscErrorCode :: ierr   
 SNESConvergedReason :: reason
 external :: &
   SNESSolve, &
! solve BVP 
 call SNESSolve(snes,PETSC_NULL_OBJECT,solution_vec,ierr)
 CHKERRQ(ierr)
end function BasicPETSc_solution
!--------------------------------------------------------------------------------------------------
!> @brief forms the basic residual vector
!--------------------------------------------------------------------------------------------------
subroutine BasicPETSC_formResidual(in,x_scal,f_scal,dummy,ierr)

 implicit none
 DMDALocalInfo, dimension(DMDA_LOCAL_INFO_SIZE) :: &
   in
 PetscScalar, dimension(3,3, &
   XG_RANGE,YG_RANGE,ZG_RANGE), intent(in) :: &
   x_scal
 PetscScalar, dimension(3,3, &
   X_RANGE,Y_RANGE,Z_RANGE), intent(out) :: &
   f_scal
! constructing residual
…..
….

 f_scal = tensorField_real(1:3,1:3,1:grid(1),1:grid(2),1:grid3)

end subroutine BasicPETSc_formResidual
!--------------------------------------------------------------------------------------------------

end module spectral_mech_basic
!--------------------------------------------------------------------------------------------------

Best regards,
Luv

> On 3 Nov 2016, at 01:17, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> 
>  Is anyone away of cases where PETSc has been used with spectral methods?
> 
>   Thanks
> 
>    Barry
> 
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