Modyfing variables

Introduction

Afivo supports cell-centered and face-centered variables. When calling m_a2_core::a2_init() a user selects how many of these variables to include. Users can modify these variables in different ways, as explained below.

Changing variables on a single box

A single box contains an array cc with cell-centered variables and an array fc with face centered variables, see the definition in m_a2_types::box2_t. These variables can be modified as shown below:

subroutine change_values(box)
   type(box2_t), intent(inout) :: box
   integer                     :: i, j

   ! Loop over the cells
   do j = 1, box%n_cell
      do i = 1, box%n_cell
         ! Set cell-centered variable 1
         box%cc(i, j, 1) = i + j + 1.0

         ! Set cell-centered variable 2
         box%cc(i, j, 2) = i - j - 1.0

         ! Set face-centered variable 1 in the x-direction
         box%fc(i, j, 1, 1) = 1.0

         ! Set face-centered variable 1 in the y-direction
         box%fc(i, j, 2, 1) = 0.0
      end do
   end do
end subroutine change_values

Calling a routine on all boxes of the tree

If a user has written a routine as shown above, then this routine can be passed to m_a2_utils::a2_loop_box:

call a2_loop_box(tree, change_values)

The routine will then be called on all the boxes of the tree. See m_a2_utils for alternatives to a2_loop_box.

Manually looping over all the boxes in a tree

A user can also manually loop over all the boxes in a tree to perform some operations. A user can for example loop over all the leaves (boxes without children) like this:

do lvl = 1, tree%highest_lvl
   do i = 1, size(tree%lvls(lvl)%leaves)
      id = tree%lvls(lvl)%leaves(i)
      call change_values(tree%boxes(id))
   end do
end do

For simplicity, OpenMP commands for parallelization have been omitted in this example.