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Java example source code file (NeighbourhoodSizeFunctionFactory.java)

This example Java source code file (NeighbourhoodSizeFunctionFactory.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

exponentialdecayfunction, neighbourhoodsizefunction, neighbourhoodsizefunctionfactory, quasisigmoiddecayfunction

The NeighbourhoodSizeFunctionFactory.java Java example source code

/*
 * 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.commons.math3.ml.neuralnet.sofm;

import org.apache.commons.math3.ml.neuralnet.sofm.util.ExponentialDecayFunction;
import org.apache.commons.math3.ml.neuralnet.sofm.util.QuasiSigmoidDecayFunction;
import org.apache.commons.math3.util.FastMath;

/**
 * Factory for creating instances of {@link NeighbourhoodSizeFunction}.
 *
 * @since 3.3
 */
public class NeighbourhoodSizeFunctionFactory {
    /** Class contains only static methods. */
    private NeighbourhoodSizeFunctionFactory() {}

    /**
     * Creates an exponential decay {@link NeighbourhoodSizeFunction function}.
     * It will compute <code>a e-x / b,
     * where {@code x} is the (integer) independent variable and
     * <ul>
     *  <li>a = initValue
     *  <li>b = -numCall / ln(valueAtNumCall / initValue)
     * </ul>
     *
     * @param initValue Initial value, i.e.
     * {@link NeighbourhoodSizeFunction#value(long) value(0)}.
     * @param valueAtNumCall Value of the function at {@code numCall}.
     * @param numCall Argument for which the function returns
     * {@code valueAtNumCall}.
     * @return the neighbourhood size function.
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if {@code initValue <= 0}.
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if {@code valueAtNumCall <= 0}.
     * @throws org.apache.commons.math3.exception.NumberIsTooLargeException
     * if {@code valueAtNumCall >= initValue}.
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if {@code numCall <= 0}.
     */
    public static NeighbourhoodSizeFunction exponentialDecay(final double initValue,
                                                             final double valueAtNumCall,
                                                             final long numCall) {
        return new NeighbourhoodSizeFunction() {
            /** DecayFunction. */
            private final ExponentialDecayFunction decay
                = new ExponentialDecayFunction(initValue, valueAtNumCall, numCall);

            /** {@inheritDoc} */
            public int value(long n) {
                return (int) FastMath.rint(decay.value(n));
            }
        };
    }

    /**
     * Creates an sigmoid-like {@code NeighbourhoodSizeFunction function}.
     * The function {@code f} will have the following properties:
     * <ul>
     *  <li>{@code f(0) = initValue}
     *  <li>{@code numCall} is the inflexion point
     *  <li>{@code slope = f'(numCall)}
     * </ul>
     *
     * @param initValue Initial value, i.e.
     * {@link NeighbourhoodSizeFunction#value(long) value(0)}.
     * @param slope Value of the function derivative at {@code numCall}.
     * @param numCall Inflexion point.
     * @return the neighbourhood size function.
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if {@code initValue <= 0}.
     * @throws org.apache.commons.math3.exception.NumberIsTooLargeException
     * if {@code slope >= 0}.
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if {@code numCall <= 0}.
     */
    public static NeighbourhoodSizeFunction quasiSigmoidDecay(final double initValue,
                                                              final double slope,
                                                              final long numCall) {
        return new NeighbourhoodSizeFunction() {
            /** DecayFunction. */
            private final QuasiSigmoidDecayFunction decay
                = new QuasiSigmoidDecayFunction(initValue, slope, numCall);

            /** {@inheritDoc} */
            public int value(long n) {
                return (int) FastMath.rint(decay.value(n));
            }
        };
    }
}

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