edu.byu.nlp.math.optimize.ConvergenceCheckers.java Source code

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Here is the source code for edu.byu.nlp.math.optimize.ConvergenceCheckers.java

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/**
 * Copyright 2012 Brigham Young 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.byu.nlp.math.optimize;

import com.google.common.base.Preconditions;

/**
 * @author rah67
 *
 */
public class ConvergenceCheckers {

    private ConvergenceCheckers() {
    }

    public static ConvergenceChecker or(final ConvergenceChecker a, final ConvergenceChecker b) {
        Preconditions.checkNotNull(a);
        Preconditions.checkNotNull(b);
        return new ConvergenceChecker() {

            @Override
            public boolean isConverged(int iteration, double prev, double cur) {
                return a.isConverged(iteration, prev, cur) || b.isConverged(iteration, prev, cur);
            }

        };
    }

    public static ConvergenceChecker and(final ConvergenceChecker a, final ConvergenceChecker b) {
        Preconditions.checkNotNull(a);
        Preconditions.checkNotNull(b);
        return new ConvergenceChecker() {

            @Override
            public boolean isConverged(int iteration, double prev, double cur) {
                return a.isConverged(iteration, prev, cur) && b.isConverged(iteration, prev, cur);
            }

        };
    }

    public static ConvergenceChecker not(final ConvergenceChecker checker) {
        Preconditions.checkNotNull(checker);
        return new ConvergenceChecker() {

            @Override
            public boolean isConverged(int iteration, double prev, double cur) {
                return !isConverged(iteration, prev, cur);
            }

        };
    }

    public static ConvergenceChecker maxIterations(final int maxIterations) {
        Preconditions.checkArgument(maxIterations > 0, "maxIterations (%s) must be greater than 0", maxIterations);
        return new ConvergenceChecker() {

            @Override
            public boolean isConverged(int iteration, double prev, double cur) {
                return iteration >= maxIterations;
            }

        };
    }

    private static class RelativePercentChangeConvergenceChecker implements ConvergenceChecker {

        private final double tolerance;

        public RelativePercentChangeConvergenceChecker(double tolerance) {
            this.tolerance = tolerance;
        }

        /** {@inheritDoc} */
        @Override
        public boolean isConverged(int iteration, double prev, double cur) {
            return relativePercentChange(prev, cur) < tolerance;
        }

        private static double relativePercentChange(double prev, double cur) {
            if (Double.isInfinite(prev) && Double.isInfinite(cur)) {
                throw new IllegalArgumentException("Previous and current values are infinite");
            }
            if (Double.isNaN(prev)) {
                throw new IllegalArgumentException("Previous value is not a number");
            }
            if (Double.isNaN(cur)) {
                throw new IllegalArgumentException("Current value is not a number");

            }
            if (Double.isInfinite(prev) || Double.isInfinite(cur)) {
                return Double.POSITIVE_INFINITY;
            }

            return 2.0 * Math.abs((prev - cur) / (prev + cur));
        }

    }

    public static ConvergenceChecker relativePercentChange(double tolerance) {
        Preconditions.checkArgument(tolerance > 0.0, "tolerance (%s) must be strictly greater than 0.0", tolerance);
        return new RelativePercentChangeConvergenceChecker(tolerance);
    }
}