DiffL1NormConvergenceCriterion.java

/***********************************************************************************************************************
 * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
 *
 * 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 eu.stratosphere.test.iterative.nephele.danglingpagerank;

import eu.stratosphere.api.common.aggregators.ConvergenceCriterion;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class DiffL1NormConvergenceCriterion implements ConvergenceCriterion<PageRankStats> {

	private static final double EPSILON = 0.00005;

	private static final Log log = LogFactory.getLog(DiffL1NormConvergenceCriterion.class);

	@Override
	public boolean isConverged(int iteration, PageRankStats pageRankStats) {
		double diff = pageRankStats.diff();

		if (log.isInfoEnabled()) {
			log.info("Stats in iteration [" + iteration + "]: " + pageRankStats);
			log.info("L1 norm of the vector difference is [" + diff + "] in iteration [" + iteration + "]");
		}

		return diff < EPSILON;
	}
}