edu.cmu.cs.lti.ark.fn.optimization.LDouble.java Source code

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Here is the source code for edu.cmu.cs.lti.ark.fn.optimization.LDouble.java

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/*******************************************************************************
 * Copyright (c) 2011 Dipanjan Das 
 * Language Technologies Institute, 
 * Carnegie Mellon University, 
 * All Rights Reserved.
 * 
 * LDouble.java is part of SEMAFOR 2.0.
 * 
 * SEMAFOR 2.0 is free software: you can redistribute it and/or modify  it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or 
 * (at your option) any later version.
 * 
 * SEMAFOR 2.0 is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. 
 * 
 * You should have received a copy of the GNU General Public License along
 * with SEMAFOR 2.0.  If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package edu.cmu.cs.lti.ark.fn.optimization;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.Serializable;

import org.apache.hadoop.io.Writable;

/**
 * Log-Double. A class to represent a double value along with a boolean indicating whether 
 * the exponentiated value should be positive (true) or negative (false). 
 * 
 * @author Kevin Gimpel
 *
 */
public class LDouble implements Serializable, Writable {
    /**
     * 
     */
    private static final long serialVersionUID = -6988066946059321823L;

    public static enum IdentityElement {
        PLUS_IDENTITY, TIMES_IDENTITY
    }

    protected static double NEG_INF = Math.log(0.0);
    protected double value;
    protected boolean sign;

    /**
     * Default constructor initializes value to be the plus-identity element in the 
     * (logplus, plus) semiring. (Initialize as LDouble(0.0) for the times-identity element)
     *
     */
    public LDouble() {
        value = NEG_INF;
        sign = true;
    }

    public LDouble(IdentityElement ie) {
        if (ie == IdentityElement.PLUS_IDENTITY) {
            value = NEG_INF;
        } else if (ie == IdentityElement.TIMES_IDENTITY) {
            value = 0.0;
        } else {
            value = 0.0; // todo: use a better value here
        }
        sign = true;
    }

    public LDouble(LDouble d) {
        value = d.value;
        sign = d.sign;
    }

    public LDouble(double v) {
        value = v;
        sign = true;
    }

    public LDouble(double v, boolean s) {
        value = v;
        sign = s;
    }

    public void reset() {
        value = NEG_INF;
        sign = true;
    }

    public static LDouble convertToLogDomain(double x) {
        if (x < 0) {
            return new LDouble(Math.log(-1.0 * x), false);
        } else {
            return new LDouble(Math.log(x), true);
        }
    }

    public static void convertToLogDomain(double x, LDouble result) {
        if (x < 0) {
            result.reset(Math.log(-1.0 * x), false);
        } else {
            result.reset(Math.log(x), true);
        }
    }

    public boolean equalsZero() {
        return (value == NEG_INF);
    }

    public boolean notEqualsZero() {
        return (value != NEG_INF);
    }

    public void reset(IdentityElement ie) {
        if (ie == IdentityElement.PLUS_IDENTITY) {
            value = NEG_INF;
        } else if (ie == IdentityElement.TIMES_IDENTITY) {
            value = 0.0;
        } else {
            value = 0.0; // todo: use a better value here
        }
        sign = true;
    }

    public void reset(LDouble ld) {
        value = ld.value;
        sign = ld.sign;
    }

    public void reset(double v) {
        value = v;
        sign = true;
    }

    public void reset(double v, boolean s) {
        value = v;
        sign = s;
    }

    public boolean isPositive() {
        return sign;
    }

    public double getValue() {
        return value;
    }

    public String toString() {
        return "" + value + ", " + sign;
    }

    public String toStringConvert() {
        return "" + value + ", " + sign + "; \t " + exponentiate();
    }

    public double exponentiate() {
        double ret = Math.exp(value);
        if (sign == false) {
            ret = -1.0 * ret;
        }
        return ret;
    }

    public void readFields(DataInput in) throws IOException {
        value = in.readDouble();
        sign = in.readBoolean();
    }

    public void write(DataOutput out) throws IOException {
        out.writeDouble(value);
        out.writeBoolean(sign);
    }
}