opensim-development – Blame information for rev 1
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1 | eva | 1 | /* |
2 | * Copyright (c) Contributors, http://opensimulator.org/ |
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3 | * See CONTRIBUTORS.TXT for a full list of copyright holders. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions are met: |
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7 | * * Redistributions of source code must retain the above copyright |
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8 | * notice, this list of conditions and the following disclaimer. |
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9 | * * Redistributions in binary form must reproduce the above copyright |
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10 | * notice, this list of conditions and the following disclaimer in the |
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11 | * documentation and/or other materials provided with the distribution. |
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12 | * * Neither the name of the OpenSimulator Project nor the |
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13 | * names of its contributors may be used to endorse or promote products |
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14 | * derived from this software without specific prior written permission. |
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15 | * |
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16 | * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY |
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17 | * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
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18 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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19 | * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY |
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20 | * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
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21 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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22 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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23 | * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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24 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
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25 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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26 | */ |
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27 | |||
28 | using System; |
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29 | |||
30 | namespace OpenSim.Framework |
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31 | { |
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32 | /// <summary> |
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33 | /// Utility class that is used to find small prime numbers and test is number prime number. |
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34 | /// </summary> |
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35 | public static class PrimeNumberHelper |
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36 | { |
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37 | /// <summary> |
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38 | /// Precalculated prime numbers. |
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39 | /// </summary> |
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40 | private static readonly int[] Primes = new int[] |
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41 | { |
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42 | 3, 7, 11, 17, 23, 29, 37, 47, 59, 71, 89, 107, 131, 163, 197, 239, |
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43 | 293, 353, 431, 521, 631, 761, 919, 1103, 1327, 1597, 1931, 2333, |
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44 | 2801, 3371, 4049, 4861, 5839, 7013, 8419, 10103, 12143, 14591, |
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45 | 17519, 21023, 25229, 30293, 36353, 43627, 52361, 62851, 75431, |
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46 | 90523, 108631, 130363, 156437, 187751, 225307, 270371, 324449, |
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47 | 389357, 467237, 560689, 672827, 807403, 968897, 1162687, 1395263, |
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48 | 1674319, 2009191, 2411033, 2893249, 3471899, 4166287, 4999559, |
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49 | 5999471, 7199369 |
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50 | }; |
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51 | |||
52 | /// <summary> |
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53 | /// Get prime number that is equal or larger than <see cref="min"/>. |
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54 | /// </summary> |
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55 | /// <param name="min"> |
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56 | /// Minimal returned prime number. |
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57 | /// </param> |
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58 | /// <returns> |
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59 | /// Primer number that is equal or larger than <see cref="min"/>. If <see cref="min"/> is too large, return -1. |
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60 | /// </returns> |
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61 | public static int GetPrime(int min) |
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62 | { |
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63 | if (min <= 2) |
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64 | return 2; |
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65 | |||
66 | if (Primes[ Primes.Length - 1 ] < min) |
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67 | { |
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68 | for (int i = min | 1 ; i < 0x7FFFFFFF ; i += 2) |
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69 | { |
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70 | if (IsPrime(i)) |
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71 | return i; |
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72 | } |
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73 | |||
74 | return -1; |
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75 | } |
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76 | |||
77 | for (int i = Primes.Length - 2 ; i >= 0 ; i--) |
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78 | { |
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79 | if (min == Primes[ i ]) |
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80 | return min; |
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81 | |||
82 | if (min > Primes[ i ]) |
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83 | return Primes[ i + 1 ]; |
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84 | } |
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85 | |||
86 | return 2; |
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87 | } |
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88 | |||
89 | /// <summary> |
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90 | /// Just basic Sieve of Eratosthenes prime number test. |
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91 | /// </summary> |
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92 | /// <param name="candinate"> |
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93 | /// Number that is tested. |
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94 | /// </param> |
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95 | /// <returns> |
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96 | /// true, if <see cref="candinate"/> is prime number; otherwise false. |
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97 | /// </returns> |
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98 | public static bool IsPrime(int candinate) |
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99 | { |
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100 | if ((candinate & 1) == 0) |
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101 | |||
102 | // Even number - only prime if 2 |
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103 | return candinate == 2; |
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104 | |||
105 | int upperBound = (int) Math.Sqrt(candinate); |
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106 | for (int i = 3 ; i < upperBound ; i += 2) |
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107 | { |
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108 | if (candinate % i == 0) |
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109 | return false; |
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110 | } |
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111 | |||
112 | return true; |
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113 | } |
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114 | } |
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115 | } |