:align: center
:alt: Keras & TensorFlow Logo
:height: 120px
:target: https://keras.io

:backlinks: none
:local: true

import os

from filelock import FileLock
from tensorflow.keras.datasets import mnist

from ray import tune
from ray.tune.schedulers import AsyncHyperBandScheduler
from ray.tune.integration.keras import TuneReportCheckpointCallback


def train_mnist(config):
    # https://github.com/tensorflow/tensorflow/issues/32159
    import tensorflow as tf

    batch_size = 128
    num_classes = 10
    epochs = 12

    with FileLock(os.path.expanduser("~/.data.lock")):
        (x_train, y_train), (x_test, y_test) = mnist.load_data()
    x_train, x_test = x_train / 255.0, x_test / 255.0
    model = tf.keras.models.Sequential(
        [
            tf.keras.layers.Flatten(input_shape=(28, 28)),
            tf.keras.layers.Dense(config["hidden"], activation="relu"),
            tf.keras.layers.Dropout(0.2),
            tf.keras.layers.Dense(num_classes, activation="softmax"),
        ]
    )

    model.compile(
        loss="sparse_categorical_crossentropy",
        optimizer=tf.keras.optimizers.SGD(learning_rate=config["learning_rate"], momentum=config["momentum"]),
        metrics=["accuracy"],
    )

    model.fit(
        x_train,
        y_train,
        batch_size=batch_size,
        epochs=epochs,
        verbose=0,
        validation_data=(x_test, y_test),
        callbacks=[TuneReportCheckpointCallback(metrics={"accuracy": "accuracy"})],
    )


def tune_mnist():
    sched = AsyncHyperBandScheduler(
        time_attr="training_iteration", max_t=400, grace_period=20
    )

    tuner = tune.Tuner(
        tune.with_resources(train_mnist, resources={"cpu": 2, "gpu": 0}),
        tune_config=tune.TuneConfig(
            metric="accuracy",
            mode="max",
            scheduler=sched,
            num_samples=10,
        ),
        run_config=tune.RunConfig(
            name="exp",
            stop={"accuracy": 0.99},
        ),
        param_space={
            "threads": 2,
            "learning_rate": tune.uniform(0.001, 0.1),
            "momentum": tune.uniform(0.1, 0.9),
            "hidden": tune.randint(32, 512),
        },
    )
    results = tuner.fit()
    return results

    

results = tune_mnist()
print(f"Best hyperparameters found were: {results.get_best_result().config} | Accuracy: {results.get_best_result().metrics['accuracy']}")

Best hyperparameters found were:  {'threads': 2, 'learning_rate': 0.07607440973606909, 'momentum': 0.7715363277240616, 'hidden': 452} | Accuracy: 0.98458331823349