/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.ignite.examples.ml.tree.boosting;

import org.apache.ignite.Ignite;
import org.apache.ignite.IgniteCache;
import org.apache.ignite.Ignition;
import org.apache.ignite.cache.affinity.rendezvous.RendezvousAffinityFunction;
import org.apache.ignite.configuration.CacheConfiguration;
import org.apache.ignite.ml.composition.boosting.GDBModel;
import org.apache.ignite.ml.composition.boosting.GDBTrainer;
import org.apache.ignite.ml.composition.boosting.convergence.mean.MeanAbsValueConvergenceCheckerFactory;
import org.apache.ignite.ml.dataset.feature.extractor.Vectorizer;
import org.apache.ignite.ml.dataset.feature.extractor.impl.DoubleArrayVectorizer;
import org.apache.ignite.ml.math.primitives.vector.VectorUtils;
import org.apache.ignite.ml.tree.boosting.GDBRegressionOnTreesTrainer;
import org.jetbrains.annotations.NotNull;

/**
 * Example represents a solution for the task of regression learning based on Gradient Boosting on trees implementation.
 * It shows an initialization of {@link GDBRegressionOnTreesTrainer}, initialization of Ignite Cache, learning step and
 * comparing of predicted and real values.
 * <p>
 * In this example dataset is created automatically by parabolic function {@code f(x) = x^2}.</p>
 */
public class GDBOnTreesRegressionTrainerExample {
    /**
     * Run example.
     *
     * @param args Command line arguments, none required.
     */
    public static void main(String... args) {
        System.out.println();
        System.out.println(">>> GDB regression trainer example started.");
        // Start ignite grid.
        try (Ignite ignite = Ignition.start("examples/config/example-ignite.xml")) {
            System.out.println(">>> Ignite grid started.");

            // Create cache with training data.
            CacheConfiguration<Integer, double[]> trainingSetCfg = createCacheConfiguration();
            IgniteCache<Integer, double[]> trainingSet = null;
            try {
                trainingSet = fillTrainingData(ignite, trainingSetCfg);

                // Create regression trainer.
                GDBTrainer trainer = new GDBRegressionOnTreesTrainer(1.0, 2000, 1, 0.)
                    .withCheckConvergenceStgyFactory(new MeanAbsValueConvergenceCheckerFactory(0.001));

                // Train decision tree model.
                GDBModel mdl = trainer.fit(
                    ignite,
                    trainingSet,
                    new DoubleArrayVectorizer<Integer>().labeled(Vectorizer.LabelCoordinate.LAST)
                );

                System.out.println(">>> ---------------------------------");
                System.out.println(">>> | Prediction\t| Valid answer \t|");
                System.out.println(">>> ---------------------------------");

                // Calculate score.
                for (int x = -5; x < 5; x++) {
                    double predicted = mdl.predict(VectorUtils.of(x));

                    System.out.printf(">>> | %.4f\t\t| %.4f\t\t|\n", predicted, Math.pow(x, 2));
                }

                System.out.println(">>> ---------------------------------");
                System.out.println(">>> GDB regression trainer example completed.");
            }
            finally {
                trainingSet.destroy();
            }
        }
        finally {
            System.out.flush();
        }
    }

    /**
     * Create cache configuration.
     */
    @NotNull private static CacheConfiguration<Integer, double[]> createCacheConfiguration() {
        CacheConfiguration<Integer, double[]> trainingSetCfg = new CacheConfiguration<>();
        trainingSetCfg.setName("TRAINING_SET");
        trainingSetCfg.setAffinity(new RendezvousAffinityFunction(false, 10));
        return trainingSetCfg;
    }

    /**
     * Fill parabolic training data.
     *
     * @param ignite         Ignite instance.
     * @param trainingSetCfg Training set config.
     */
    @NotNull private static IgniteCache<Integer, double[]> fillTrainingData(Ignite ignite,
        CacheConfiguration<Integer, double[]> trainingSetCfg) {
        IgniteCache<Integer, double[]> trainingSet = ignite.getOrCreateCache(trainingSetCfg);
        for (int i = -50; i <= 50; i++) {
            double x = ((double)i) / 10.0;
            double y = Math.pow(x, 2);
            trainingSet.put(i, new double[] {x, y});
        }
        return trainingSet;
    }
}
