check_res Subroutine

  subroutine check_res( varname, res, error )
    ! ---------------------------------------------------------------------- !
    character(len=labelLen), intent(in) :: varname
    real(kind=rk), intent(in) :: res(:)
    integer, intent(out) :: error
    ! ---------------------------------------------------------------------- !
    integer :: iElem  
    real(kind=rk) :: diff_dens(nElems_track)
    real(kind=rk) :: diff_state(nElems_track,4)
    real(kind=rk) :: diff_vel(nElems_track,3)
    ! ---------------------------------------------------------------------- !
    error = 0 
    select case (trim(varname))
    case ('state')
      do iElem = 1, nElems_track
        diff_state(iElem,:) = res((iElem-1)*4 + 1 : (iElem-1)*4 + 4 ) &
          &                 - state(iElem,:)
      end do    
      if ( any(diff_state > eps) ) then
        error = -1
        write(*,*) 'Refernece value for state does not match'
      end if  
      if (dumpRes) then
        do iElem = 1, nElems_track
          write(*,*) 'reference: ', state(iElem, :)
          write(*,*) '   output: ', res( (iElem-1)*4 + 1 : (iElem-1)*4 + 4 )
        end do
      end if  
    case ('density')
      diff_dens = res(:) - dens
      if ( any(diff_dens > eps) ) then
        error = -1
        write(*,*) 'Refernece value for density does not match'
      end if  
      if (dumpRes) then
        write(*,*) 'reference: ', dens
        write(*,*) '   output: ', res
      end if  
    case ('velocity')
      do iElem = 1, nElems_track
        diff_vel(iElem,:) = res((iElem-1)*3 + 1 : (iElem-1)*3 + 3 ) &
          &               - vel(iElem,:)
      end do
      if ( any(diff_vel > eps) ) then
        error = -1
        write(*,*) 'Refernece value for velocity does not match'
      end if  
      if (dumpRes) then
        do iElem = 1, nElems_track
          write(*,*) 'reference: ', vel(iElem, :)
          write(*,*) '   output: ', res( (iElem-1)*3 + 1 : (iElem-1)*3 + 3 )
        end do  
      end if  
    case default
      write(*,*) 'Unknown variable name', trim(varname)
      error = -1
    end select
      
   end subroutine check_res