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guma_random.h

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00001 /* LIBGUL - Geometry Utility Library
00002  * Copyright (C) 1998-1999 Norbert Irmer
00003  *
00004  * This library is free software; you can redistribute it and/or
00005  * modify it under the terms of the GNU Library General Public
00006  * License as published by the Free Software Foundation; either
00007  * version 2 of the License, or (at your option) any later version.
00008  *
00009  * This library is distributed in the hope that it will be useful,
00010  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012  * Library General Public License for more details.
00013  *
00014  * You should have received a copy of the GNU Library General Public
00015  * License along with this library; if not, write to the
00016  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
00017  * Boston, MA 02111-1307, USA.
00018  */
00019 
00020 #ifndef GUMA_RANDOM_H
00021 #define GUMA_RANDOM_H
00022 
00023 namespace guma {
00024 
00025 /*----------------------------------------------------------------------------
00026   System dependent function to get a seed for pseudo random number generators
00027 ----------------------------------------------------------------------------*/
00028 GULAPI gul::uint32 GetSeed();
00029 
00030 /*------------------------------------------------------------------
00031   Function for generating pseudo random numbers with DES crypto
00032 ------------------------------------------------------------------*/
00033 GULAPI void PseudoDes( gul::uint32 *lword, gul::uint32 *irword );
00034 
00035 /*------------------------------------------------------------------
00036   Class which can be used as a parameter for templates which need a
00037   random number generator
00038 ------------------------------------------------------------------*/
00039 class random_des
00040 {
00041 public:
00042   GULAPI static gul::uint32 cycle;
00043   GULAPI static gul::uint32 sequence;
00044   GULAPI static bool initialized;
00045 
00046   // can be used for debugging to with a certain sequence/cycle
00047   static double des_random( bool reset, gul::uint32 *idum )
00048   {
00049     const double factor = 1.0/((double)LL(0x100000000));
00050     gul::uint32 irword,lword;
00051   
00052     if( reset )
00053     {
00054       sequence = *idum;
00055       *idum = 1;
00056     }
00057     irword = *idum;
00058     lword = sequence;
00059 
00060     PseudoDes( &lword, &irword );
00061 
00062     (*idum)++;
00063 
00064     return ((double)irword) * factor;
00065   }
00066 
00067   static double Random( void )
00068   {
00069     if( !initialized )
00070     {
00071       initialized = true;
00072       cycle = GetSeed();
00073       return des_random( true, &cycle );
00074     }
00075     return des_random( false, &cycle );
00076   }
00077 };
00078 
00079 }
00080 
00081 #endif

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