check_laguerre_weights Subroutine

  subroutine check_laguerre_weights (wgt, eps)
    use file_utils, only: error_unit
    use mp, only: mp_abort
    implicit none
    real, intent (in) :: eps
    real, dimension (:), intent (in) :: wgt
    logical :: error=.false.
    integer :: imax, n
    real :: s

    n = size(wgt)

    ! check if weights are all positive
    if (any(wgt <= 0.0)) then
       write (error_unit(),*) 'ERROR in laguerre: weights are not positive at n =', n
       error = .true.
    end if

    ! check if there is a single maximum
    imax = sum(maxloc(wgt))
    if (any(wgt(1:imax-1) > wgt(2:imax))) then
       write (error_unit(),*) 'ERROR in laguerre: weights decreasing before maximum'
       error = .true.
    end if
    if (any(wgt(imax:n-1) < wgt(imax+1:n))) then
       write (error_unit(),*) 'ERROR in laguerre: weights increasing after maximum'
       error = .true.
    end if

    ! check if their sum is close enough to normalized value
    if (debug) then
       s = sum(dble(wgt))
       if (abs(s-1.0) > eps) then
          write (error_unit(),*) 'WARNING in laguerre: weights summation incorrect:', &
               size(wgt), s
          ! Do not stop as it is mostly a minor issue
       end if
    end if

    if (error) call mp_abort ('STOP error in check_laguerre_weights')

  end subroutine check_laguerre_weights