SpaceOpt: hyperparameter optimization via gradient boosting regression

SpaceOpt is a hyperparameter optimization algorithm that uses gradient boosting regression to find the most promising candidates for the next trial by predicting their evaluation score.

Installation

$ pip install spaceopt

Usage

1. Define a discrete hyperparameter search space, for example:

search_space = {
    'a': [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],  # list of ordered numbers: ints
    'b': [-3.5, -0.1, 0.0, 2.5, 10.0],    # list of ordered numbers: floats
    'c': [256, 512, 1024, 2048],          # another list of ordered numbers
    'd': ['ABC', 'IJK', 'XYZ'],           # categorical variable
    'e': [True, False],                   # boolean variable
    # ... (add as many as you need)
}

2. Define your evaluation function:

def evaluation_function(spoint: dict) -> float:
    # your code (e.g. model fit)
    return y  # score (e.g. model accuracy)

spoint = {'a': 4, 'b': 0.0, 'c': 512, 'd': 'XYZ', 'e': False}
y = evaluation_function(spoint)

3. Use SpaceOpt for a hyperparameter optimization:

from spaceopt import SpaceOpt

spaceopt = SpaceOpt(search_space=search_space,
                    target_name='y',
                    objective='maximize')  # or 'minimize'

for iteration in range(200):
    if iteration < 20:
        spoint = spaceopt.get_random()     # exploration
    else:
        spoint = spaceopt.fit_predict()    # exploitation

    spoint['y'] = evaluation_function(spoint)
    spaceopt.append_evaluated_spoint(spoint)

More examples here.

Advanced

• get multiple points by setting num_spoints:

spoints = spaceopt.get_random(num_spoints=2)
# or
spoints = spaceopt.fit_predict(num_spoints=5)

• control exploration vs. exploitation behaviour by adjusting sample_size (default=10000), which is the number of candidates sampled for ranking:

spoint = spaceopt.fit_predict(sample_size=1000)  # decreasing `sample_size` increses exploration
spoint = spaceopt.fit_predict(sample_size=100000)  # increasing `sample_size` increses exploitation

• add manually selected evaluation points to SpaceOpt:

my_spoint = {'a': 8, 'b': -3.5, 'c': 256, 'd': 'IJK', 'e': False}
my_spoint['y'] = evaluation_function(my_spoint)
spaceopt.append_evaluated_spoint(my_spoint)

• learn more by reading the code, there are only 3 classes: SpaceOpt, Space and Variable.

License

MIT License (see LICENSE).