[petsc-users] Field wise residual norm

[Dharmendar Reddy]

I may need to read more about those functions to see how i can get the
norms. But a quick look seem to suggest me that i will need lesser
function calls than what i am thinking of doing right now.

This is how my approach...Am i doing it right ?

subroutine computeResidualNorm(meshDM,F,fieldId,fNorm)
  implicit none
#include "finclude/petsc.h90"
  ! IO Variables
  DM, intent(inout) :: meshDM
  Vec, intent(inout) :: F
  integer, intent(in ) :: fieldId
  real(WP), intent(inout) :: fNorm

  ! Local Variables
  PetscErrorCode :: ierr
  PetscSection :: Section
  PetscScalar, pointer :: FArray(:)
  Vec :: gVec, lVec
  PetscScalar, pointer :: lArray(:)
  integer :: numFieldDof,offset,dofId
  integer :: CellId,CellIdStart,CellIdEnd
  PetscScalar :: zero

  zero = 0.0_WP
  call DMGetGlobalVector(meshDM, gVec, ierr)
  call DMGetLocalVector(meshDM, lVec, ierr)
  call Vecset(lVec, zero, ierr)

  ! Get acess to default section
  call DMGetDefaultSection(meshDM,section,ierr)
  ! Get chart
  call  PetscSectionGetChart(section,cellIdstart,CellIdEnd,ierr)
  call vecGetArrayF90(F, FArray, ierr)
  call VecGetArrayF90(lVec, lArray, ierr)
  do cellId=cellIdstart,cellIdEnd-1
    call PetscSectionGetFieldDof(section,CellId,fieldId,numFieldDof,ierr)
    if(numFieldDof > 0) then
      call PetscSectionGetFieldOffset(section,cellId,fieldId,offset,ierr)
      do dofId=0,numFieldDof-1
        ic = offset+dofId
        lArray(ic) = FArray(ic)
      end do
    end if
  end do
  call VecRestoreArrayF90(lVec, lArray, ierr)
  call vecRestoreArrayF90(F, Farray,ierr)

  call DMLocalToGlobalBegin(meshDM, lVec, INSERT_VALUES, gVec, ierr)
  call DMLocalToGlobalEnd(meshDM, lVec, INSERT_VALUES, gVec, ierr)

  call DMRestoreLocalVector(meshDM, lVec, ierr)

  call VecNorm( gVec, NORM_2, fNorm, ierr)

  call DMRestoreGlobalVector(meshDM, gVec, ierr)
end subroutine computeResidualNorm

On Mon, Jan 13, 2014 at 4:15 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Mon, Jan 13, 2014 at 4:11 PM, Dharmendar Reddy <dharmareddy84 at gmail.com>
> wrote:
>>
>> Hello,
>>         Is there a petsc function which can help accomplish the following:
>> I am solving a coupled system of equations:
>>
>> F1(x1,x2,x3) = 0
>>
>> F2(x1,x2,x3) = 0
>>
>> F3(x1,x2,x3) = 0
>>
>>
>> I am using DMPlex to handle to mesh data. I would like to compute the
>> norm of residual of each function.
>>
>> I assemble the function element wise. I am looking for some interface
>> like,
>> ComputNorm(dm, F, fieldIndex).
>
>
> Our thinking is generally that you would use
>
>   DMCreateSubDM()
>
> and then use VecScatterCreate() with the IS it returns. This will map F into
> one of the F1/F2/F3.
>
> Does this make sense?
>
>    Matt
>
>>
>> Thanks
>> Reddy
>
>
>
>
> --
> 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



-- 
-----------------------------------------------------
Dharmendar Reddy Palle
Graduate Student
Microelectronics Research center,
University of Texas at Austin,
10100 Burnet Road, Bldg. 160
MER 2.608F, TX 78758-4445
e-mail: dharmareddy84 at gmail.com
Phone: +1-512-350-9082
United States of America.
Homepage: https://webspace.utexas.edu/~dpr342