randgenerator.h

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/**********************************************************************
 *<
    FILE: RandGenerator.h

    DESCRIPTION: Generator of random numbers

    CREATED BY: Oleg Bayborodin

    HISTORY: Nov.17 2000 - created

    GOALS: To solve the need in satisfactory generator of random numbers.

    DESCRIPTION: The class has interfaces for srand/rand methods of VC++ 
        and other functions for random number generation.

        Srand/rand methods from stdlib.h have two main problems:
        a) It's not satisfactory random. Since rand() function returns a 
            pseudorandom integer in the range 0 to 0x7fff=32767, if we
            need a lot of random numbers (i.e. for generating 100,000 
            particles), we are running out of continuity of random num-
            bers. Generated random numbers became too discrete.
        b) rand() method is global function, not class object. Hence it's
            shared between all modules of your plug-in. Changes in one
            module may change randomness pattern in other independent 
            module. To solve this contradiction, rand methods have to be
            implemented as a class object.

        RandGenerator does exactly that. It has much more random numbers:
        RAND_MAX = 0xFFFFFFFF = 4,294,967,295. Also, using instance of 
        the class, it's much easier to create separate thread of random 
        numbers for specific module.

 *> Copyright (c) 2000, All Rights Reserved.
 **********************************************************************/

#pragma once
#include <WTypes.h>
#include "coreexp.h"
#include "maxheap.h"


// to fix conflict between RandGenerator and stdlib.h do the following:
#undef RAND_MAX
const unsigned int RAND_MAX = 0x7fff; // as defined in stdlib.h

class RandGenerator: public MaxHeapOperators 
{
    public:
        CoreExport RandGenerator(); // constructor
    
    // override for VC++ rand methods
        CoreExport static const DWORD32 RAND_MAX;

        // The srand function sets the starting point for generating a 
        // series of pseudorandom integers. To reinitialize the generator, 
        // use 1 as the seed argument. Any other value for seed sets the 
        // generator to a random starting point. rand() retrieves the 
        // pseudorandom numbers that are generated. Calling rand() before 
        // any call to srand() generates the same sequence as calling srand() 
        // with seed passed as 1.
        CoreExport void srand(DWORD32 seed);
        // The rand function returns a pseudorandom integer in the range 0 to RAND_MAX
        CoreExport DWORD32 rand( void );

    // other useful functions:
        CoreExport int      RandSign( void );
        CoreExport float    Rand01( void );
        CoreExport float    Rand11( void );
        CoreExport float    Rand55( void );
        CoreExport int      Rand0X(int maxnum);

        const bool  Valid( void ) const { 
            return m_explicitelyInitialized; 
        }

    private:
        static const DWORD32 kMagicNumber1, kMagicNumber2;
        static const DWORD32 HALF_RAND_MAX;
        static const double kIntMax, kIntMax1, kHalfIntMax;
        DWORD32 m_randar[256];
        DWORD32 m_randX, m_randY;
        bool m_explicitelyInitialized;
};