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src/biu/RandomNumberGenerator.cc

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#include "biu/RandomNumberGenerator.hh"
#include <stdlib.h>
#include <biu/assertbiu.hh>

namespace biu {


    
    
    RNG_ISO::RNG_ISO(unsigned int seed_) : RandomNumberGenerator(seed_)
    {
        setSeed(seed_);
    }
    
    RNG_ISO::~RNG_ISO()
    {}
    
    void 
    RNG_ISO::setSeed(unsigned int _seed)
    {
        seed = _seed;
        srand(_seed);
    }
    
    unsigned int 
    RNG_ISO::getRN()
    {
        return rand();
    }
    
    unsigned int 
    RNG_ISO::getMaxRN() {
        return RAND_MAX;
    }
    
    RandomNumberGenerator* 
    RNG_ISO::copy(void) {
        return new RNG_ISO(*this);
    }
    
    
    
    
    
    
    
    
    
    
    RNG_LCG::RNG_LCG(unsigned int seed_) : RandomNumberGenerator(seed_)
    {
        setSeed(seed_);
    }
    
    RNG_LCG::~RNG_LCG()
    {}
    
    
    void 
    RNG_LCG::setSeed(unsigned int _seed)
    {
        assertbiu(_seed > 0, "seed value has to be > zero!");
        seed = _seed;
    }
    
    unsigned int 
    RNG_LCG::getRN()
    {
        
        // Wikipedia: using 64 bit integer arithmetics to compute 32 bit integer
        // V_{j+1} = (279470273 * V_j) % 4294967291
        //  
        //        uint64_t z;
        //        z = a;
        //        z *= 279470273; 
        //        z %= 4294967291U;
        //        a = z;
        //        return a;
        
        // same algorithm using shift operations
        // taken from rand_r.c (glibc 2.5)
        unsigned int next = seed;
        int result;
    
        next *= 1103515245;
        next += 12345;
        result = (unsigned int) (next / 65536) % 2048;
    
        next *= 1103515245;
        next += 12345;
        result <<= 10;
        result ^= (unsigned int) (next / 65536) % 1024;
    
        next *= 1103515245;
        next += 12345;
        result <<= 10;
        result ^= (unsigned int) (next / 65536) % 1024;
    
        seed = next;
        
        return result;
    }

    unsigned int 
    RNG_LCG::getMaxRN() {
        return 2147483647;
    }
    
    RandomNumberGenerator* 
    RNG_LCG::copy(void) {
        return new RNG_LCG(*this);
    }
    

} // namespace biu