This function murmur hashes an integer value. - Java java.lang

Java examples for java.lang:Math Value

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Description

This function murmur hashes an integer value.

Demo Code

/*// w  ww . j  a  v a  2s.c  om
 * 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 com.java2s;

public class Main {
    /**
     * This function hashes an integer value.
     *
     * It is crucial to use different hash functions to partition data across machines and the internal partitioning of
     * data structures. This hash function is intended for partitioning across machines.
     *
     * @param code The integer to be hashed.
     * @return The non-negative hash code for the integer.
     */
    public static int murmurHash(int code) {
        code *= 0xcc9e2d51;
        code = Integer.rotateLeft(code, 15);
        code *= 0x1b873593;

        code = Integer.rotateLeft(code, 13);
        // By the MurmurHash algorithm the following should be "code = code * 5 + 0xe6546b64;" (see FLINK-3623)
        // but correcting the algorithm is a breaking change (see FLINK-4154). The effect of the resulting skew
        // increases with increased parallelism (see FLINK-4154).
        code *= 0xe6546b64;

        code ^= 4;
        code ^= code >>> 16;
        code *= 0x85ebca6b;
        code ^= code >>> 13;
        code *= 0xc2b2ae35;
        code ^= code >>> 16;

        if (code >= 0) {
            return code;
        } else if (code != Integer.MIN_VALUE) {
            return -code;
        } else {
            return 0;
        }
    }
}

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