Check-in commons-math 3.6.1 am: 1354beaf45 am: 0018f64b87 am: b3715644fb am: 5484895ffd

Original change: https://android-review.googlesource.com/c/platform/external/apache-commons-math/+/2702413

Change-Id: Idb04c8014ec76e9930d6d0aa22dac3b0b54333c8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

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
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+++ b/src/main/java/org/apache/commons/math3/util/RandomPivotingStrategy.java
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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.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);
+    }
+}