/**
* 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.mahout.clustering.lda;
/**
* Various utility classes for doing LDA inference..
*/
final class LDAUtil {
private LDAUtil() { } // no creation
/**
* @return log(exp(a) + exp(b))
*/
static double logSum(double a, double b) {
return a == Double.NEGATIVE_INFINITY ? b : b == Double.NEGATIVE_INFINITY ? a
: a < b ? b + Math.log1p(Math.exp(a - b)) : a + Math.log1p(Math.exp(b - a));
}
}