/**
* Copyright (C) 2001-3, Anthony Harrison anh23@pitt.edu This library is free
* software; you can redistribute it and/or modify it under the terms of the GNU
* Lesser General Public License as published by the Free Software Foundation;
* either version 2.1 of the License, or (at your option) any later version.
* This library 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 Lesser General Public License for more
* details. You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package org.jactr.core.module.retrieval.time;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jactr.core.chunk.IChunk;
import org.jactr.core.logging.Logger;
import org.jactr.core.module.retrieval.four.IRetrievalModule4;
/**
* 4.0 retrieval time equation
*
* @author harrison
* @created April 18, 2003
*/
public class DefaultRetrievalTimeEquation implements IRetrievalTimeEquation
{
private static transient Log LOGGER = LogFactory
.getLog(DefaultRetrievalTimeEquation.class
.getName());
IRetrievalModule4 _retrievalModule;
IChunk _errorChunk;
boolean _warned = false;
public DefaultRetrievalTimeEquation(IRetrievalModule4 module)
{
_retrievalModule = module;
}
/**
* Description of the Method
*
* @param model
* Description of the Parameter
* @param chunk
* Description of the Parameter
* @return Description of the Return Value
*/
public double computeRetrievalTime(IChunk chunk)
{
double latencyFactor = _retrievalModule.getLatencyFactor();
double latencyExponent = _retrievalModule.getLatencyExponent();
double threshold = _retrievalModule.getRetrievalThreshold();
double retrievalTime = 0;
if (_errorChunk == null)
_errorChunk = _retrievalModule.getModel().getDeclarativeModule()
.getErrorChunk();
if (chunk.equals(_errorChunk))
{
/*
* if the retrieval threshold is inf, the time at which the retrieval will
* fail will be inf as well, so we need to return something a little less
* dangerous - so we use the error chunk activation to compute the
* retrieval time.
*/
if (Double.isInfinite(threshold) || Double.isNaN(threshold))
{
retrievalTime = latencyFactor *
Math.exp(-_errorChunk.getSubsymbolicChunk().getActivation());
if (!_warned)
{
StringBuilder msg = new StringBuilder(
"since retrieval threshold is not active, retrieval errors can take an infinite time. Returning in ");
msg.append(retrievalTime).append("s instead.");
if (LOGGER.isWarnEnabled()) LOGGER.warn(msg);
msg.insert(0, "Warning ");
if (Logger.hasLoggers(_retrievalModule.getModel()))
Logger.log(_retrievalModule.getModel(), Logger.Stream.RETRIEVAL,
msg.toString());
_warned = true;
}
}
else
// otherwise, we fail using the normal math
retrievalTime = latencyFactor * Math.exp(-threshold);
}
else
{
/*
* everything is fine, calculate the retrieval time bsed on the chunks
* activation
*/
double activation = chunk.getSubsymbolicChunk().getActivation();
retrievalTime = latencyFactor * Math.exp(-latencyExponent * activation);
}
return retrievalTime;
}
}