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Random.d

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00001 /*******************************************************************************
00002 
00003         @file Random.d
00004         
00005         Copyright (c) 2004 Kris Bell
00006         
00007         This software is provided 'as-is', without any express or implied
00008         warranty. In no event will the authors be held liable for damages
00009         of any kind arising from the use of this software.
00010         
00011         Permission is hereby granted to anyone to use this software for any 
00012         purpose, including commercial applications, and to alter it and/or 
00013         redistribute it freely, subject to the following restrictions:
00014         
00015         1. The origin of this software must not be misrepresented; you must 
00016            not claim that you wrote the original software. If you use this 
00017            software in a product, an acknowledgment within documentation of 
00018            said product would be appreciated but is not required.
00019 
00020         2. Altered source versions must be plainly marked as such, and must 
00021            not be misrepresented as being the original software.
00022 
00023         3. This notice may not be removed or altered from any distribution
00024            of the source.
00025 
00026         4. Derivative works are permitted, but they must carry this notice
00027            in full and credit the original source.
00028 
00029 
00030                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00031 
00032         
00033         @version        Initial version, April 2004      
00034         @author         various
00035 
00036 
00037 *******************************************************************************/
00038 
00039 module mango.utils.Random;
00040 
00041 
00042 /******************************************************************************
00043 
00044         KISS (via George Marsaglia & Paul Hsieh)
00045 
00046         the idea is to use simple, fast, individually promising
00047         generators to get a composite that will be fast, easy to code
00048         have a very long period and pass all the tests put to it.
00049         The three components of KISS are
00050 
00051                 x(n)=a*x(n-1)+1 mod 2^32
00052                 y(n)=y(n-1)(I+L^13)(I+R^17)(I+L^5),
00053                 z(n)=2*z(n-1)+z(n-2) +carry mod 2^32
00054 
00055         The y's are a shift register sequence on 32bit binary vectors
00056         period 2^32-1; The z's are a simple multiply-with-carry sequence 
00057         with period 2^63+2^32-1.  
00058 
00059         The period of KISS is thus 2^32*(2^32-1)*(2^63+2^32-1) > 2^127
00060 
00061 ******************************************************************************/
00062 
00063 version (Win32)
00064         {
00065         extern(Windows) int QueryPerformanceCounter (ulong *);
00066         }
00067 
00068 version (Posix)
00069         {
00070                 version (linux)
00071                          private import std.c.linux.linux;
00072 
00073                 version (darwin)
00074                          private import std.c.darwin.darwin;
00075         }
00076 
00077 class Random
00078 {
00079         private static uint kiss_x = 1;
00080         private static uint kiss_y = 2;
00081         private static uint kiss_z = 4;
00082         private static uint kiss_w = 8;
00083         private static uint kiss_carry = 0;
00084         private static uint kiss_k;
00085         private static uint kiss_m;
00086 
00087         /**********************************************************************
00088 
00089         **********************************************************************/
00090 
00091         static this () 
00092         {
00093                 ulong s;
00094 
00095                 version (Posix)
00096                         {           
00097                         timeval tv;
00098 
00099                         gettimeofday (&tv, null);
00100                         s = tv.tv_usec;
00101                         }
00102                 version (Win32)
00103                          QueryPerformanceCounter (&s);
00104 
00105                 seed (s);
00106         }
00107 
00108         /**********************************************************************
00109 
00110         **********************************************************************/
00111 
00112         static final void seed (uint seed) 
00113         {
00114                 kiss_x = seed | 1;
00115                 kiss_y = seed | 2;
00116                 kiss_z = seed | 4;
00117                 kiss_w = seed | 8;
00118                 kiss_carry = 0;
00119         }
00120 
00121         /**********************************************************************
00122 
00123         **********************************************************************/
00124 
00125         static final uint get (uint limit)
00126         {
00127                 return get() % limit;
00128         }
00129 
00130         /**********************************************************************
00131 
00132         **********************************************************************/
00133 
00134         static final uint get ()
00135         {
00136                 kiss_x = kiss_x * 69069 + 1;
00137                 kiss_y ^= kiss_y << 13;
00138                 kiss_y ^= kiss_y >> 17;
00139                 kiss_y ^= kiss_y << 5;
00140                 kiss_k = (kiss_z >> 2) + (kiss_w >> 3) + (kiss_carry >> 2);
00141                 kiss_m = kiss_w + kiss_w + kiss_z + kiss_carry;
00142                 kiss_z = kiss_w;
00143                 kiss_w = kiss_m;
00144                 kiss_carry = kiss_k >> 30;
00145                 return kiss_x + kiss_y + kiss_w;
00146         }
00147 }
00148 

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