[16218] | 1 | #region License Information
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| 2 | /* HeuristicLab
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[16662] | 3 | * Copyright (C) 2002-2019 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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[16218] | 4 | *
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| 5 | * This file is part of HeuristicLab.
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| 6 | *
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| 7 | * HeuristicLab is free software: you can redistribute it and/or modify
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| 8 | * it under the terms of the GNU General Public License as published by
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| 9 | * the Free Software Foundation, either version 3 of the License, or
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| 10 | * (at your option) any later version.
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| 11 | *
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| 12 | * HeuristicLab is distributed in the hope that it will be useful,
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| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 15 | * GNU General Public License for more details.
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| 16 | *
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| 17 | * You should have received a copy of the GNU General Public License
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| 18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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| 19 | */
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| 20 | #endregion
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| 21 |
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| 22 |
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[16272] | 23 | using System;
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| 24 | using System.Security.Cryptography;
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| 25 |
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[16218] | 26 | namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
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| 27 | public static class HashUtil {
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| 28 | // This class contains some hash functions adapted from http://partow.net/programming/hashfunctions/index.html#AvailableHashFunctions
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| 29 |
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| 30 | // A simple hash function from Robert Sedgwicks Algorithms in C book.I've added some simple optimizations to the algorithm in order to speed up its hashing process.
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[16272] | 31 | public static ulong RSHash(byte[] input) {
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[16218] | 32 | const int b = 378551;
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[16263] | 33 | ulong a = 63689;
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| 34 | ulong hash = 0;
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[16218] | 35 |
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| 36 | foreach (var v in input) {
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| 37 | hash = (hash * a) + v;
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| 38 | a *= b;
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| 39 | }
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| 40 | return hash;
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| 41 | }
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| 42 |
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| 43 | // A bitwise hash function written by Justin Sobel
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[16272] | 44 | public static ulong JSHash(byte[] input) {
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[16263] | 45 | ulong hash = 1315423911;
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[16218] | 46 | for (int i = 0; i < input.Length; ++i)
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| 47 | hash ^= (hash << 5) + input[i] + (hash >> 2);
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| 48 | return hash;
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| 49 | }
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| 50 |
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| 51 | // This hash function comes from Brian Kernighan and Dennis Ritchie's book "The C Programming Language". It is a simple hash function using a strange set of possible seeds which all constitute a pattern of 31....31...31 etc, it seems to be very similar to the DJB hash function.
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[16272] | 52 | public static ulong BKDRHash(byte[] input) {
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[16263] | 53 | ulong seed = 131;
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| 54 | ulong hash = 0;
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[16218] | 55 | foreach (var v in input) {
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| 56 | hash = (hash * seed) + v;
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| 57 | }
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| 58 | return hash;
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| 59 | }
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| 60 |
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| 61 | // This is the algorithm of choice which is used in the open source SDBM project. The hash function seems to have a good over-all distribution for many different data sets. It seems to work well in situations where there is a high variance in the MSBs of the elements in a data set.
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[16272] | 62 | public static ulong SDBMHash(byte[] input) {
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[16263] | 63 | ulong hash = 0;
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[16218] | 64 | foreach (var v in input) {
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| 65 | hash = v + (hash << 6) + (hash << 16) - hash;
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| 66 | }
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| 67 | return hash;
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| 68 | }
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| 69 |
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| 70 | // An algorithm produced by Professor Daniel J. Bernstein and shown first to the world on the usenet newsgroup comp.lang.c. It is one of the most efficient hash functions ever published.
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[16272] | 71 | public static ulong DJBHash(byte[] input) {
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[16263] | 72 | ulong hash = 5381;
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[16218] | 73 | foreach (var v in input) {
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| 74 | hash = (hash << 5) + hash + v;
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| 75 | }
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| 76 | return hash;
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| 77 | }
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| 78 |
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| 79 | // An algorithm proposed by Donald E.Knuth in The Art Of Computer Programming Volume 3, under the topic of sorting and search chapter 6.4.
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[16272] | 80 | public static ulong DEKHash(byte[] input) {
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[16263] | 81 | ulong hash = (ulong)input.Length;
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[16218] | 82 | foreach (var v in input) {
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| 83 | hash = (hash << 5) ^ (hash >> 27) ^ v;
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| 84 | }
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| 85 | return hash;
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| 86 | }
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| 87 |
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[16272] | 88 | public static ulong CryptoHash(HashAlgorithm ha, byte[] input) {
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| 89 | return BitConverter.ToUInt64(ha.ComputeHash(input), 0);
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| 90 | }
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[16218] | 91 | }
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| 92 | }
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