def METHOD_NAME(self, t):
    fd, fh, bbox, pfix, args = self.domain.params
    dptol, ttol = self.params
    point = self.mesh.point
    N = point.shape[0]
    A, B = self.get_iterate_matrix()
    D = spdiags(1.0/A.diagonal(), 0, N, N)
    C = -(triu(A, 1) + tril(A, -1))
    X = D*(C*point[:, 0] - B*point[:, 1])
    Y = D*(B*point[:, 0] + C*point[:, 1])
    dxdt = np.zeros((N, 2), dtype=np.float)
    dxdt[:,0] = X - point[:,0]
    dxdt[:,1] = Y - point[:,1]
    if pfix is not None:
        dxdt[0:pfix.shape[0],:] = 0
    return dxdt 