bayesian_optimization_multicore.py

#!/usr/bin/env python3
 
 
 
# A simple example to use bayesian optimization for the hyperparameters of a FastBDT.
# The package used in this example is https://github.com/scikit-optimize
# and can be installed with
# pip3 install scikit-optimize
 
from basf2 import find_file
import basf2_mva
import basf2_mva_util
import skopt
from skopt.space import Integer
from sklearn.externals.joblib import Parallel, delayed
import matplotlib.pyplot as plt
 
 
def f(x, general_options, process_number):
    """Returns the figure of merit for the optimization.
    The functions trains the classifier with the given hyperparameters on the training sample and
    calculates the AUC on the independent test sample.
    """
    g_options = general_options
    g_options.m_identifier = f"test{process_number}.xml"
    options = basf2_mva.FastBDTOptions()
    options.m_nTrees = int(x[0])
    options.m_nLevels = int(x[1])
    basf2_mva.teacher(g_options, options)
    m = basf2_mva_util.Method(g_options.m_identifier)
    p, t = m.apply_expert(test_data, general_options.m_treename)
    return -basf2_mva_util.calculate_auc_efficiency_vs_background_retention(p, t)
 
 
if __name__ == "__main__":
    train_file = find_file("mva/train_D0toKpipi.root", "examples")
    test_file = find_file("mva/test_D0toKpipi.root", "examples")
 
    training_data = basf2_mva.vector(train_file)
    test_data = basf2_mva.vector(test_file)
 
    general_options = basf2_mva.GeneralOptions()
    general_options.m_datafiles = training_data
    general_options.m_treename = "tree"
    general_options.m_variables = basf2_mva.vector('p', 'pz', 'daughter(0, kaonID)', 'chiProb', 'M')
    general_options.m_target_variable = "isSignal"
 
    # init optimizer
    optimizer = skopt.Optimizer(dimensions=[Integer(10, 1000), Integer(2, 6)], n_initial_points=3)
 
    # calculate initial guess
    initial_guess = [10, 2]
    initial_res = f(initial_guess, general_options, 0)
    optimizer.tell(initial_guess, initial_res)
 
    # optimize
    for i in range(10):
        x = optimizer.ask(n_points=2)  # x is a list of n_points points
        y = Parallel(n_jobs=-1)(delayed(f)(v, general_options, index) for index, v in enumerate(x))  # evaluate points in parallel
        res = optimizer.tell(x, y)
 
    # Give some results
    print(res)
    skopt.plots.plot_convergence(res)
    plt.savefig('convergence.png')
    skopt.plots.plot_evaluations(res)
    plt.savefig('evaluations.png')
    skopt.plots.plot_objective(res)
    plt.savefig('objective.png')
 
    # Store result of optimization
    skopt.dump(res, 'opt-result.pkl')