/*
 * 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.selection.scoring;

import java.io.IOException;
import org.apache.ignite.Ignite;
import org.apache.ignite.IgniteCache;
import org.apache.ignite.Ignition;
import org.apache.ignite.examples.ml.util.MLSandboxDatasets;
import org.apache.ignite.examples.ml.util.SandboxMLCache;
import org.apache.ignite.ml.dataset.feature.extractor.Vectorizer;
import org.apache.ignite.ml.dataset.feature.extractor.impl.DummyVectorizer;
import org.apache.ignite.ml.knn.regression.KNNRegressionModel;
import org.apache.ignite.ml.knn.regression.KNNRegressionTrainer;
import org.apache.ignite.ml.knn.utils.indices.SpatialIndexType;
import org.apache.ignite.ml.math.distances.ManhattanDistance;
import org.apache.ignite.ml.math.primitives.vector.Vector;
import org.apache.ignite.ml.selection.scoring.evaluator.Evaluator;
import org.apache.ignite.ml.selection.scoring.metric.MetricName;

/**
 * Run kNN regression trainer ({@link KNNRegressionTrainer}) over distributed dataset.
 * <p>
 * After that it trains the model based on the specified data using
 * <a href="https://en.wikipedia.org/wiki/K-nearest_neighbors_algorithm">kNN</a> regression algorithm.</p>
 * <p>
 * Finally, this example loops over the test set of data points, applies the trained model to predict what cluster does
 * this point belong to, and compares prediction to expected outcome (ground truth).</p>
 * <p>
 * You can change the test data used in this example or trainer object settings and re-run it to explore this algorithm
 * further.</p>
 */
public class RegressionMetricExample {
    /**
     * Run example.
     */
    public static void main(String[] args) throws IOException {
        System.out.println();
        System.out.println(">>> kNN regression over cached dataset usage example started.");
        // Start ignite grid.
        try (Ignite ignite = Ignition.start("examples/config/example-ignite.xml")) {
            System.out.println(">>> Ignite grid started.");

            IgniteCache<Integer, Vector> dataCache = null;
            try {
                dataCache = new SandboxMLCache(ignite).fillCacheWith(MLSandboxDatasets.CLEARED_MACHINES);

                KNNRegressionTrainer trainer = new KNNRegressionTrainer()
                    .withK(5)
                    .withDistanceMeasure(new ManhattanDistance())
                    .withIdxType(SpatialIndexType.BALL_TREE)
                    .withWeighted(true);

                Vectorizer<Integer, Vector, Integer, Double> vectorizer = new DummyVectorizer<Integer>()
                    .labeled(Vectorizer.LabelCoordinate.FIRST);

                KNNRegressionModel knnMdl = trainer.fit(ignite, dataCache, vectorizer);

                double mae = Evaluator.evaluate(dataCache,
                    knnMdl, vectorizer, MetricName.MAE
                );

                System.out.println("\n>>> Mae " + mae);
            }
            finally {
                if (dataCache != null)
                    dataCache.destroy();
            }
        }
        finally {
            System.out.flush();
        }
    }
}
