UT_MTwister.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        UT_MTwister.h ( UT Library, C++)
 *
 * COMMENTS:    The Mersenne Twister
 *
 *  The Mersenne Twister code is licensed under GNU and includes the following
 *  notice:
 * 
 *      Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
 *      All rights reserved.
 * 
 */

#ifndef __UT_Random__
#define __UT_Random__

#include "UT_API.h"
#include <SYS/SYS_Types.h>
#include <SYS/SYS_Math.h>
#include <iosfwd>

class UT_IStream;

class UT_API UT_MersenneTwister {
public:
     UT_MersenneTwister(uint seed=5489U)
     {
        setSeed(seed);
     }
    ~UT_MersenneTwister() {}

    void                setSeed(uint seed);
    void                setSeed(const uint key[], uint klength);

    void                save(std::ostream &os, bool binary) const;
    // Returns true if successful and false otherwise.
    bool                load(UT_IStream &is);

    // Unsigned integer random number generation
    uint                urandom()
                        {
                            uint        y;
                            if (myIndex == 624)
                            {
                                y = doReload();
                                myIndex = 1;
                            }
                            else
                            {
                                y = myState[myIndex++];
                            }

                            y ^= (y >> 11);
                            y ^= (y <<  7) & 0x9d2c5680U;
                            y ^= (y << 15) & 0xefc60000U;
                            return (y ^ (y >> 18));
                        }

    // Floating point generation:  range := [0, 1)
    fpreal32            frandom()
                        {
                            SYS_FPRealUnionF    tmp;
                            tmp.uval = 0x3f800000 | (0x007fffff & urandom());
                            return tmp.fval - CONST_FPREAL32(1.0);
                        }
    // Floating point generation:  range := [-.5, .5)
    fpreal32            frandom0()
                        {
                            SYS_FPRealUnionF    tmp;
                            tmp.uval = 0x3f800000 | (0x007fffff & urandom());
                            return tmp.fval - CONST_FPREAL32(1.5);
                        }
private:
    uint        doReload();

    uint        myIndex;
    uint        myState[625];
};

#endif