def truncate_paths(paths, max_samples):
    """
    Truncate the list of paths so that the total number of samples is exactly equal to max_samples. This is done by
    removing extra paths at the end of the list, and make the last path shorter if necessary
    :param paths: a list of paths
    :param max_samples: the absolute maximum number of samples
    :return: a list of paths, truncated so that the number of samples adds up to max-samples
    """
    # chop samples collected by extra paths
    # make a copy
    paths = list(paths)
    total_n_samples = sum(len(path["rewards"]) for path in paths)
    while len(paths) > 0 and total_n_samples - len(paths[-1]["rewards"]) >= max_samples:
        total_n_samples -= len(paths.pop(-1)["rewards"])
    if len(paths) > 0:
        last_path = paths.pop(-1)
        truncated_last_path = dict()
        truncated_len = len(last_path["rewards"]) - (total_n_samples + max_samples)
        for k, v in last_path.iteritems():
            if k in ["observations", "actions", "rewards"]:
                truncated_last_path[k] = tensor_utils.truncate_tensor_list(v, truncated_len)
            elif k in ["env_infos", "agent_infos"]:
                truncated_last_path[k] = tensor_utils.truncate_tensor_dict(v, truncated_len)
            else:
                raise NotImplementedError
        paths.append(truncated_last_path)
    return paths
dataset/ETHPy150Open rllab/rllab/rllab/sampler/parallel_sampler.py/truncate_paths/operator `-` -> `+`