code: def choose_ncv(k):
      """
      Choose number of lanczos vectors based on target number
      of singular/eigen values and vectors to compute, k.
      """
      return max(2 * k + 1, 20)
  
imports: import numpy
  import warnings
  from scipy.sparse.linalg._interface import aslinearoperator, LinearOperator
  from scipy.sparse import eye, issparse
  from scipy.linalg import eig, eigh, lu_factor, lu_solve
  from scipy.sparse._sputils import isdense, is_pydata_spmatrix
  from scipy.sparse.linalg import gmres, splu
  from scipy._lib._util import _aligned_zeros
  from scipy._lib._threadsafety import ReentrancyLock
  from .None import _arpack
label_desc: Use image node_id 1 for calling a global function with example usage: choose_ncv(k) and returns: max