HyperBand Function Example

#!/usr/bin/env python

import argparse
import json
import os

import numpy as np

import ray
from ray import train, tune
from ray.train import Checkpoint
from ray.tune.schedulers import HyperBandScheduler


def train_func(config, checkpoint_dir=None):
    step = 0
    if checkpoint_dir:
        with open(os.path.join(checkpoint_dir, "checkpoint")) as f:
            step = json.loads(f.read())["timestep"]

    for timestep in range(step, 100):
        v = np.tanh(float(timestep) / config.get("width", 1))
        v *= config.get("height", 1)

        # Checkpoint the state of the training every 3 steps
        # Note that this is only required for certain schedulers
        checkpoint = None
        if timestep % 3 == 0:
            checkpoint = Checkpoint.from_dict({"timestep": timestep})

        # Here we use `episode_reward_mean`, but you can also report other
        # objectives such as loss or accuracy.
        train.report({"episode_reward_mean": v}, checkpoint=checkpoint)


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--smoke-test", action="store_true", help="Finish quickly for testing"
    )
    args, _ = parser.parse_known_args()

    ray.init(num_cpus=4 if args.smoke_test else None)

    # Hyperband early stopping, configured with `episode_reward_mean` as the
    # objective and `training_iteration` as the time unit,
    # which is automatically filled by Tune.
    hyperband = HyperBandScheduler(max_t=200)

    tuner = tune.Tuner(
        train_func,
        run_config=train.RunConfig(
            name="hyperband_test",
            stop={"training_iteration": 10 if args.smoke_test else 99999},
            failure_config=train.FailureConfig(
                fail_fast=True,
            ),
        ),
        tune_config=tune.TuneConfig(
            num_samples=20,
            metric="episode_reward_mean",
            mode="max",
            scheduler=hyperband,
        ),
        param_space={"height": tune.uniform(0, 100)},
    )
    results = tuner.fit()
    print("Best hyperparameters found were: ", results.get_best_result().config)