modules/ml/src/main/java/org/apache/ignite/ml/selection/paramgrid/ParameterSetGenerator.java

/*
 * 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.ml.selection.paramgrid;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;

/**
 * Generates tuples of hyper parameter values by given map.
 *
 * In the given map keys are names of hyper parameters
 * and values are arrays of values for hyper parameter presented in the key.
 */
public class ParameterSetGenerator {
    /** Size of parameter vector. Default value is 100. */
    private int sizeOfParamVector = 100;

    /** Params. */
    private List<Double[]> params = new ArrayList<>();

    /** The given map of hyper parameters and its values. */
    private Map<Integer, Double[]> map;

    /**
     * Creates an instance of the generator.
     *
     * @param map In the given map keys are names of hyper parameters
     * and values are arrays of values for hyper parameter presented in the key.
     */
    public ParameterSetGenerator(Map<Integer, Double[]> map) {
        assert map != null;
        assert !map.isEmpty();

        this.map = map;
        sizeOfParamVector = map.size();
    }

    /**
     * Returns the list of tuples presented as arrays.
     */
    public List<Double[]> generate() {

        Double[] nextPnt = new Double[sizeOfParamVector];

        traverseTree(map, nextPnt, -1);

        return Collections.unmodifiableList(params);
    }

    /**
     * Traverse tree on the current level and starts procedure of child traversing.
     *
     * @param map The current state of the data.
     * @param nextPnt Next point.
     * @param dimensionNum Dimension number.
     */
    private void traverseTree(Map<Integer, Double[]> map, Double[] nextPnt, int dimensionNum) {
        dimensionNum++;

        if (dimensionNum == sizeOfParamVector){
            Double[] paramSet = Arrays.copyOf(nextPnt, sizeOfParamVector);
            params.add(paramSet);
            return;
        }

        Double[] valuesOfCurrDimension = map.get(dimensionNum);

        for (Double specificValue : valuesOfCurrDimension) {
            nextPnt[dimensionNum] = specificValue;
            traverseTree(map, nextPnt, dimensionNum);
        }
    }
}