    def merge_shards(self) -> None:
        """Merges all shard files into shard 0, then removes shard suffix."""

        shard_id = self.data_parallel_rank
        num_shards = self.data_parallel_world_size

        if self.data_parallel_world_size > 1:

            def merge_shards_with_root(fname: str) -> None:
                fname = os.path.join(self.cfg.decoding.results_path, fname)
                logger.info("Merging %s on shard %d", fname, shard_id)
                base_fpath = Path(f"{fname}.0")
                with open(base_fpath, "a") as out_file:
                    for s in range(1, num_shards):
                        shard_fpath = Path(f"{fname}.{s}")
                        with open(shard_fpath, "r") as in_file:
                            for line in in_file:
                                out_file.write(line)
                        shard_fpath.unlink()
                shutil.move(f"{fname}.0", fname)

            dist.barrier()  # ensure all shards finished writing
            if shard_id == (0 % num_shards):
                merge_shards_with_root("hypo.word")
            if shard_id == (1 % num_shards):
                merge_shards_with_root("hypo.units")
            if shard_id == (2 % num_shards):
                merge_shards_with_root("ref.word")
            if shard_id == (3 % num_shards):
                merge_shards_with_root("ref.units")
            dist.barrier()
Merges all shard files into shard 0, then removes shard suffix.
examples/speech_recognition/new/infer.py