anchor.diff:          call runge_kutta(dt, t0, u0, op, n, order, iters, u, pumping, coeffs)
       end subroutine solve_nls
   
  -end module nls
  +end module nls
positive.code:         end if
      end subroutine make_laplacian
  
      subroutine rgbmv(x, u, sign, op, klu, n) ! reduced gbmv()
          implicit none
  
  
negative.code:         call sgbmv('N', n, n, klu, klu, sign, op, 2 * klu + 1, x, 1, 1.0, u, 1)
      end subroutine rgbmv
  
      !   \brief Calculate density of revervoir particles with given pumping profile and condensate density.
      !
      !   \param[in] pumping
      !   \verbatim
      !       Pumping profile on spacial grid.
      !   \endverbatim
      !
      !   \param[in] coeffs
      !   \verbatim
      !       Contains coefficients of NLS equation with reservoir. Each coefficient coresponds to each term of NLS
      !       equation or exciton-polariton revervoir. See `solve_nls`.
      !   \endverbatim
      !
      !   \param[in] u_sqr
      !   \verbatim
      !       Squared absolute value of psi-function.
      !   \endverbatim
      !
      !   \param[out] r
      !   \verbatim
      !       Density of revervoir particles.
      !   \endverbatim
      !
      !   \param[in] n
      !   \verbatim
      !       Number of nodes of spacial grid.
      !   \endverbatim
      subroutine revervoir(pumping, coeffs, u_sqr, r, n)
          implicit none
  
  