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/**
 * 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.ctakes.ytex.kernel.metric;

import java.util.Map;

public class LCHMetric extends BaseSimilarityMetric {
	/**
	 * log(max depth * 2)
	 */
	double logdm = 0d;

	@Override
	public double similarity(String concept1, String concept2,
			Map conceptFilter, SimilarityInfo simInfo) {
		if (logdm != 0d) {
			initLCSes(concept1, concept2, simInfo);
			if (simInfo.getLcsDist() > 0) {
				// double lch = logdm - Math.log((double) simInfo.getLcsDist());
				// // scale to depth
				// return lch / logdm;
				return 1 - (Math.log((double) simInfo.getLcsDist()) / logdm);
			}
		}
		return 0d;
	}

	public LCHMetric(ConceptSimilarityService simSvc, Integer maxDepth) {
		super(simSvc);
		if (maxDepth != null) {
			this.logdm = Math.log(2 * maxDepth);
		}
	}

}