Tpetra parallel linear algebra Version of the Day
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Tpetra_Details_Hash.cpp
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4//
5// Tpetra: Templated Linear Algebra Services Package
6// Copyright (2008) Sandia Corporation
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43
44#include "Tpetra_Details_Hash.hpp"
45
46namespace Tpetra {
47namespace Details {
48namespace Impl {
49
50int getRecommendedSizeInt (const int size)
51{
52 // A large list of prime numbers.
53 // Based on a recommendation by Andres Valloud in hash forums.
54 // There are only enough primes here so that between any number N and 2*N,
55 // there will be at least about 8 to choose from (except the first 10).
56 // This is a balance between a small list of primes, and getting a
57 // collection size that doesn't waste too much space. In addition,
58 // the primes in this table were chosen so that they do not divide
59 // 256^k +- a, for 1<=k<=8, and -32<=a<=32. This is so that
60 // using them as a modulo will not have a tendency to just throw away
61 // the most significant bits of the object's hash. The primes (except the
62 // first ten) or not close to any power of two to avoid aliasing
63 // between hash functions based on bit manipulation and the moduli.
64 int primes [ ] = {
65 3, 7, 13, 23, 53, 97, 193, 389, 769, 1543,
66 2237, 2423, 2617, 2797, 2999, 3167, 3359, 3539,
67 3727, 3911, 4441 , 4787 , 5119 , 5471 , 5801 , 6143 , 6521 , 6827
68 , 7177 , 7517 , 7853 , 8887 , 9587 , 10243 , 10937 , 11617 , 12289
69 , 12967 , 13649 , 14341 , 15013 , 15727
70 , 17749 , 19121 , 20479 , 21859 , 23209 , 24593 , 25939 , 27329
71 , 28669 , 30047 , 31469 , 35507 , 38231 , 40961 , 43711 , 46439
72 , 49157 , 51893 , 54617 , 57347 , 60077 , 62801 , 70583 , 75619
73 , 80669 , 85703 , 90749 , 95783 , 100823 , 105871 , 110909 , 115963
74 , 120997 , 126031 , 141157 , 151237 , 161323 , 171401 , 181499 , 191579
75 , 201653 , 211741 , 221813 , 231893 , 241979 , 252079
76 , 282311 , 302483 , 322649 , 342803 , 362969 , 383143 , 403301 , 423457
77 , 443629 , 463787 , 483953 , 504121 , 564617 , 604949 , 645313 , 685609
78 , 725939 , 766273 , 806609 , 846931 , 887261 , 927587 , 967919 , 1008239
79 , 1123477 , 1198397 , 1273289 , 1348177 , 1423067 , 1497983 , 1572869
80 , 1647761 , 1722667 , 1797581 , 1872461 , 1947359 , 2022253
81 , 2246953 , 2396759 , 2546543 , 2696363 , 2846161 , 2995973 , 3145739
82 , 3295541 , 3445357 , 3595117 , 3744941 , 3894707 , 4044503
83 , 4493921 , 4793501 , 5093089 , 5392679 , 5692279 , 5991883 , 6291469
84 , 6591059 , 6890641 , 7190243 , 7489829 , 7789447 , 8089033
85 , 8987807 , 9586981 , 10186177 , 10785371 , 11384539 , 11983729
86 , 12582917 , 13182109 , 13781291 , 14380469 , 14979667 , 15578861
87 , 16178053 , 17895707 , 19014187 , 20132683 , 21251141 , 22369661
88 , 23488103 , 24606583 , 25725083 , 26843549 , 27962027 , 29080529
89 , 30198989 , 31317469 , 32435981 , 35791397 , 38028379 , 40265327
90 , 42502283 , 44739259 , 46976221 , 49213237 , 51450131 , 53687099
91 , 55924061 , 58161041 , 60397993 , 62634959 , 64871921
92 , 71582857 , 76056727 , 80530643 , 85004567 , 89478503 , 93952427
93 , 98426347 , 102900263 , 107374217 , 111848111 , 116322053 , 120795971
94 , 125269877 , 129743807 , 143165587 , 152113427 , 161061283 , 170009141
95 , 178956983 , 187904819 , 196852693 , 205800547 , 214748383 , 223696237
96 , 232644089 , 241591943 , 250539763 , 259487603 , 268435399 };
97
98 int hsize = primes[220] ;
99 for (int i = 0; i < 221; ++i) {
100 if (size <= primes[i]) {
101 hsize = primes[i];
102 break;
103 }
104 }
105 return hsize;
106}
107
108} // namespace Impl
109} // namespace Details
110} // namespace Tpetra
Implementation details of Tpetra.
Namespace Tpetra contains the class and methods constituting the Tpetra library.