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Diffstat (limited to 'src/main/java/org/apache/commons/math3/util/RandomPivotingStrategy.java')
-rw-r--r-- | src/main/java/org/apache/commons/math3/util/RandomPivotingStrategy.java | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/util/RandomPivotingStrategy.java b/src/main/java/org/apache/commons/math3/util/RandomPivotingStrategy.java new file mode 100644 index 0000000..f2fc28b --- /dev/null +++ b/src/main/java/org/apache/commons/math3/util/RandomPivotingStrategy.java @@ -0,0 +1,58 @@ +/* + * 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.commons.math3.util; + +import org.apache.commons.math3.exception.MathIllegalArgumentException; +import org.apache.commons.math3.random.RandomGenerator; + +import java.io.Serializable; + +/** + * A strategy of selecting random index between begin and end indices. + * + * @since 3.4 + */ +public class RandomPivotingStrategy implements PivotingStrategyInterface, Serializable { + + /** Serializable UID. */ + private static final long serialVersionUID = 20140713L; + + /** Random generator to use for selecting pivot. */ + private final RandomGenerator random; + + /** + * Simple constructor. + * + * @param random random generator to use for selecting pivot + */ + public RandomPivotingStrategy(final RandomGenerator random) { + this.random = random; + } + + /** + * {@inheritDoc} A uniform random pivot selection between begin and end indices + * + * @return The index corresponding to a random uniformly selected value between first and the + * last indices of the array slice + * @throws MathIllegalArgumentException when indices exceeds range + */ + public int pivotIndex(final double[] work, final int begin, final int end) + throws MathIllegalArgumentException { + MathArrays.verifyValues(work, begin, end - begin); + return begin + random.nextInt(end - begin - 1); + } +} |