Example for using a synthetic BoTorch test function in a discrete searchspace

This example assumes some basic familiarity with using BayBE. We thus refer to campaign for a basic example.

Necessary imports for this example

import numpy as np
from botorch.test_functions import Rastrigin

from baybe import Campaign
from baybe.objective import Objective
from baybe.parameters import NumericalDiscreteParameter
from baybe.searchspace import SearchSpace
from baybe.targets import NumericalTarget
from baybe.utils.botorch_wrapper import botorch_function_wrapper

Defining the test function

BoTorch offers a variety of different test functions, all of which can be used. Note that some test functions are only defined for specific dimensions. If the dimension you provide is not available for the chose function, a warning will be printed. In addition, the dimension is then adjusted automatically.

Note that choosing a different test function requires to change the import statement. All test functions that are available in BoTorch are also available here and are later wrapped via the botorch_function_wrapper.

DIMENSION = 4
TestFunctionClass = Rastrigin

This code checks if the test function is only available for a specific dimension. In that case, we print a warning and replace DIMENSION. In addition, it constructs the actual TestFunction object.

if not hasattr(TestFunctionClass, "dim"):
    TestFunction = TestFunctionClass(dim=DIMENSION)
elif TestFunctionClass().dim == DIMENSION:
    TestFunction = TestFunctionClass()
else:
    print(
        f"\nYou choose a dimension of {DIMENSION} for the test function"
        f"{TestFunctionClass}. However, this function can only be used in "
        f"{TestFunctionClass().dim} dimension, so the provided dimension is replaced. "
        "Also, DISC_INDICES and CONT_INDICES will be re-written."
    )
    TestFunction = TestFunctionClass()
    DIMENSION = TestFunctionClass().dim
    DISC_INDICES = list(range(0, (DIMENSION + 1) // 2))
    CONT_INDICES = list(range((DIMENSION + 1) // 2, DIMENSION))

BoTorch provides reasonable bounds for the variables which are used to define the searchspace.

BOUNDS = TestFunction.bounds

It is necessary to “translate” the BoTorch function such that it can be used by BayBE. This is done by using the botorch_function_wrapper function.

WRAPPED_FUNCTION = botorch_function_wrapper(test_function=TestFunction)

Creating the searchspace and the objective

In this example, we construct a purely discrete space. The parameter POINTS_PER_DIM controls the number of points per dimension. Note that the searchspace will have POINTS_PER_DIM**DIMENSION many points.

POINTS_PER_DIM = 4

Since we have a discrete searchspace, we only construct NumericalDiscreteParameters. We use the data of the test function to deduce bounds and number of parameters.

parameters = [
    NumericalDiscreteParameter(
        name=f"x_{k+1}",
        values=list(np.linspace(BOUNDS[0, k], BOUNDS[1, k], POINTS_PER_DIM)),
        tolerance=0.01,
    )
    for k in range(DIMENSION)
]

searchspace = SearchSpace.from_product(parameters=parameters)
objective = Objective(
    mode="SINGLE", targets=[NumericalTarget(name="Target", mode="MIN")]
)

Constructing the campaign and performing a recommendation

campaign = Campaign(
    searchspace=searchspace,
    objective=objective,
)

# Get a recommendation for a fixed batch size.
BATCH_SIZE = 3
recommendation = campaign.recommend(batch_size=BATCH_SIZE)

Evaluate the test function. Note that we need iterate through the rows of the recommendation. Furthermore, we need to interpret the row as a list.

target_values = []
for index, row in recommendation.iterrows():
    target_values.append(WRAPPED_FUNCTION(*row.to_list()))

We add an additional column with the calculated target values.

recommendation["Target"] = target_values

Here, we inform the campaign about our measurement.

campaign.add_measurements(recommendation)
print("\n\nRecommended experiments with measured values: ")
print(recommendation)

Recommended experiments with measured values: 
          x_1   x_2       x_3       x_4      Target
141  1.706667 -5.12  5.120000 -1.706667   89.053253
78  -1.706667 -5.12  5.120000  1.706667   89.053253
11  -5.120000 -5.12  1.706667  5.120000  102.376076