class_docstr: The original dataset is available at: http://corpus-texmex.irisa.fr/
  (ANN_SIFT1B)
class_docstr_tok: ["The","original","dataset","is","available","at",":","http",":","\/\/corpus-texmex.irisa.fr\/","(","ANN_SIFT1B",")"]
code: def __init__(self, nb_M=1000):
      Dataset.__init__(self)
      assert nb_M in (1, 2, 5, 10, 20, 50, 100, 200, 500, 1000)
      self.nb_M = nb_M
      nb = nb_M * 10**6
      self.d, self.nt, self.nb, self.nq = 128, 10**8, nb, 10000
      self.basedir = dataset_basedir + "bigann/"
  
imports: import os
  import numpy
  import faiss
  from .vecs_io import fvecs_read, ivecs_read, bvecs_mmap, fvecs_mmap
  from .exhaustive_search import knn
label_desc: Use image node_id 1 to create a new DatasetBigANN object from inherited base classes: Dataset with example: obj = DatasetBigANN(nb_M)