pack_indices_array Module Function

  module function pack_indices_array(a, indices, dim) result(c)
    !! Pack an autodiff array
    implicit none
    class(array_type), intent(in), target :: a
    integer, dimension(:), intent(in) :: indices
    integer, intent(in) :: dim
    type(array_type), pointer :: c

    integer :: i, s

    if(dim.eq.1)then
       c => a%create_result(array_shape=[size(indices), size(a%val,2)])
       do concurrent(s=1:size(a%val,2), i=1:size(indices))
          c%val(i, s) = a%val(indices(i), s)
       end do
    elseif(dim.eq.2)then
       c => a%create_result(array_shape=[size(a%val,1), size(indices)])
       do concurrent(s=1:size(indices), i=1:size(a%val,1))
          c%val(i, s) = a%val(i, indices(s))
       end do
    end if
    c%indices = indices
    allocate(c%adj_ja(2,1))
    c%adj_ja(:,1) = [ dim, size(a%val,dim) ]

    c%get_partial_left => get_partial_pack_indices
    c%get_partial_right => get_partial_unpack_indices
    c%get_partial_left_val => get_partial_pack_indices_val
    if(a%requires_grad) then
       c%requires_grad = .true.
       c%is_forward = a%is_forward
       c%operation = 'pack_indices'
       c%left_operand => a
       c%owns_left_operand = a%is_temporary
    end if
  end function pack_indices_array