text: #
  # Pyserini: Reproducible IR research with sparse and dense representations
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  # http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  
  import argparse
  
  import faiss
  import os
  
  
  parser = argparse.ArgumentParser()
  parser.add_argument('--dimension', type=int, help='dimension of passage embeddings', required=False, default=768)
  parser.add_argument('--prefix', type=str, help='directory to store brute force index of corpus', required=True)
  parser.add_argument('--shard-num', type=int, help='number of shards', default=1)
  args = parser.parse_args()
  
  new_index = faiss.IndexFlatIP(args.dimension)
  docid_files = []
  for i in range(args.shard_num):
      index = faiss.read_index(os.path.join(args.prefix + str(i), 'index'))
      docid_files.append(os.path.join(args.prefix + str(i), 'docid'))
      vectors = index.reconstruct_n(0, index.ntotal)
      new_index.add(vectors)
  
  if not os.path.exists(args.prefix + 'full'):
      os.mkdir(args.prefix + 'full')
  
  faiss.write_index(new_index, os.path.join(args.prefix + 'full', 'index'))
  
  with open(os.path.join(args.prefix + 'full', 'docid'), 'w') as wfd:
      for f in docid_files:
          with open(f, 'r') as f1:
              for line in f1:
                  wfd.write(line)
  