write_results_rdp Subroutine

    subroutine write_results_rdp(filename, vals, res, tol)
        !! Prints the intermediate results of iterative eigenvalue/singular value decompositions
        implicit none(type, external)
        character(len=*), intent(in) :: filename
        !! Output filename. This file will be overwritten
        real(dp), intent(in) :: vals(:)
        !! Intermediate values
        real(dp), intent(inout) :: res(:)
        !! Residuals
        real(dp), intent(in) :: tol
        !! Convergence tolerance
        ! internals
        integer :: i, k, idx
        integer, allocatable :: indices(:)
        character(len=*), parameter :: fmt = '(I6,2(2X,E16.9),2X,L4)'
        k = size(vals)
        if (io_rank()) then ! only IO rank writes
            allocate(indices(k))
            call sort_index(res, indices) ! res is returned in sorted order
            open (1234, file=filename, status='replace', action='write')
                write (1234, '(A6,2(A18),A6)') 'Iter', 'value', 'residual', 'conv'
            do i = 1, k
                idx = indices(i)
                    write (1234, fmt) k, vals(idx),                           res(i), res(i) < tol
            end do 
            close (1234)
        end if
    end subroutine write_results_rdp