text: import scipy.io
  import scipy.sparse.linalg
  
  stiffMat = scipy.io.mmread("a1-direct-poisson-8-stiffMat.mm")
  vals_X, vecs_X = scipy.sparse.linalg.eigs(stiffMat, which='LR')
  vals_N, vecs_N = scipy.sparse.linalg.eigs(stiffMat, which='SR')
  
  lam_max = vals_X[1].real # skip the positive eigenvalue
  lam_min = vals_N[5].real
  
  print( "L_max %g. L_min %g" % (lam_max, lam_min) )
  