edu.emory.mathcs.nlp.learning.util.MLUtils.java Source code

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Here is the source code for edu.emory.mathcs.nlp.learning.util.MLUtils.java

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/**
 * Copyright 2015, Emory University
 * 
 * Licensed 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 edu.emory.mathcs.nlp.learning.util;

import org.apache.commons.math3.util.FastMath;

import edu.emory.mathcs.nlp.common.util.DSUtils;
import it.unimi.dsi.fastutil.ints.IntCollection;
import it.unimi.dsi.fastutil.ints.IntIterator;

/**
 * @author Jinho D. Choi ({@code jinho.choi@emory.edu})
 */
public class MLUtils {
    /** Transform the scores into softmax regression. */
    static public void softmax(float[] scores) {
        float sum = 0;

        for (int i = 0; i < scores.length; i++) {
            scores[i] = (float) FastMath.exp(scores[i]);
            sum += scores[i];
        }

        for (int i = 0; i < scores.length; i++)
            scores[i] /= sum;
    }

    static public int argmax(float[] scores) {
        return argmax(scores, scores.length);
    }

    static public int argmax(float[] scores, int size) {
        int i, maxIndex = 0;
        double maxValue = scores[maxIndex];

        for (i = 1; i < size; i++) {
            if (maxValue < scores[i]) {
                maxIndex = i;
                maxValue = scores[maxIndex];
            }
        }

        return maxIndex;
    }

    static public int argmax(float[] scores, IntCollection labels) {
        if (labels == null || labels.isEmpty())
            return argmax(scores);
        float maxValue = -Float.MAX_VALUE;
        int maxIndex = -1;

        for (int i : labels) {
            if (maxValue < scores[i]) {
                maxIndex = i;
                maxValue = scores[i];
            }
        }

        return maxIndex;
    }

    static public int[] argmax2(float[] scores) {
        return argmax2(scores, scores.length);
    }

    static public int[] argmax2(float[] scores, int size) {
        if (size < 2)
            return new int[] { 0, -1 };
        int[] max = { 0, 1 };

        if (scores[0] < scores[1]) {
            max[0] = 1;
            max[1] = 0;
        }

        for (int i = 2; i < size; i++) {
            if (scores[max[0]] < scores[i]) {
                max[1] = max[0];
                max[0] = i;
            } else if (scores[max[1]] < scores[i])
                max[1] = i;
        }

        return max;
    }

    static public int[] argmax2(float[] scores, IntCollection labels) {
        if (labels == null || labels.isEmpty())
            return argmax2(scores);
        IntIterator it = labels.iterator();
        if (labels.size() < 2)
            return new int[] { it.nextInt(), -1 };
        int[] max = { it.nextInt(), it.nextInt() };

        if (scores[max[0]] < scores[max[1]])
            DSUtils.swap(max, 0, 1);

        while (it.hasNext()) {
            int i = it.nextInt();

            if (scores[max[0]] < scores[i]) {
                max[1] = max[0];
                max[0] = i;
            } else if (scores[max[1]] < scores[i])
                max[1] = i;
        }

        return max;
    }
}