text: import numpy
  
  from pyamg.gallery import poisson
  from pyamg.classical import CR
  from pyamg.vis import vis_splitting
  
  n = 50
  A=poisson((n,n)).tocsr()
  
  xx = numpy.arange(0,n,dtype=float)
  x,y = numpy.meshgrid(xx,xx)
  Verts = numpy.concatenate([[x.ravel()],[y.ravel()]],axis=0).T
  
  splitting = CR(A)
  vis_splitting(Verts=Verts, splitting=splitting,output='matplotlib')
  