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-rw-r--r--src/experimental/randomcmwc.cpp52
1 files changed, 52 insertions, 0 deletions
diff --git a/src/experimental/randomcmwc.cpp b/src/experimental/randomcmwc.cpp
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1/*
2 * Copyright (C) 2007-2012 Xagasoft, All rights reserved.
3 *
4 * This file is part of the libbu++ library and is released under the
5 * terms of the license contained in the file LICENSE.
6 */
7
8#include "bu/randomcmwc.h"
9
10#define PHI 0x9e3779b9
11
12RandomCmwc::RandomCmwc() :
13 q( NULL ),
14 c( 362436 )
15{
16 q = new uint32_t[4096];
17}
18
19RandomCmwc::~RandomCmwc()
20{
21 delete[] q;
22}
23
24void RandomCmwc::seed( int32_t iSeed )
25{
26 int i;
27
28 Q[0] = iSeed;
29 Q[1] = iSeed + PHI;
30 Q[2] = iSeed + PHI + PHI;
31
32 for (i = 3; i < 4096; i++)
33 Q[i] = Q[i - 3] ^ Q[i - 2] ^ PHI ^ i;
34}
35
36int32_t RandomCmwc::rand()
37{
38 uint64_t t, a = 18782LL;
39 static uint32_t i = 4095;
40 uint32_t x, r = 0xfffffffe;
41 i = (i + 1) & 4095;
42 t = a * Q[i] + c;
43 c = (t >> 32);
44 x = t + c;
45 if( x < c )
46 {
47 x++;
48 c++;
49 }
50 return (Q[i] = r - x);
51}
52