Python API basics

This short tutorial will show you the basics to use Oríon in python. We will optimize a simple 1-d rosenbrock function with random search and TPE and visualize the regret curve to compare the algorithms.

We first import the only function needed, build experiment.

from orion.client import build_experiment

We configure the database with PickledDB so that the results are saved locally on disk. This enables resuming the experiment and running parallel workers.

storage = {
    "type": "legacy",
    "database": {
        "type": "pickleddb",
        "host": "./db.pkl",
    },
}

We define the search space for the optimization. Here, the optimization algorithm may explore real values for x between 0 and 30 only. See documentation of Search Space for more information.

space = {"x": "uniform(0, 30)"}

We then build the experiment with the name random-rosenbrock. The name is by Oríon as an id for the experiment. Each experiment must have a unique name.

experiment = build_experiment(
    "random-rosenbrock",
    space=space,
    storage=storage,
)

For this example we use a 1-d rosenbrock function. We must return a list of results, for Oríon. Results must have the format {name: <str>: type: <'objective', 'constraint' or 'gradient'>, value=<float>} otherwise a ValueError will be raised. At least one of the results must have the type objective, the metric that is minimized by the algorithm.

def rosenbrock(x, noise=None):
    """Evaluate partial information of a quadratic."""
    y = x - 34.56789
    z = 4 * y ** 2 + 23.4

    return [{"name": "objective", "type": "objective", "value": z}]

We then pass the function rosenbrock to workon(). This method will iteratively try new sets of hyperparameters suggested by the optimization algorithm until it reaches 20 trials.

experiment.workon(rosenbrock, max_trials=20)

Now let’s plot the regret curve to see how well went the optimization.

experiment.plot.regret().show()