preiods.cpp

#include <iostream>
#include <time.h>
#include <math.h>
#include <map>

#define LOOPSIZE 100000

union fract_u
{
    float dval;
    unsigned char data[sizeof(double)];
};

fract_u preclevel(const fract_u& orig, unsigned int level = 0)
{
    fract_u copy;
    copy.dval = orig.dval;

    switch (level)
    {
    case 0:
        return copy;
    case 1:
        copy.data[0] = 0;
        copy.data[1] = 0;
        copy.data[2] = 0;
        return copy;
    case 2:
        copy.data[0] = 0;
        copy.data[1] = 0;
        return copy;
    case 3:
        copy.data[0] = 0;
        return copy;
    default:
        return copy;
    }
    return copy;
}

fract_u preclevel2(const fract_u& orig, unsigned int level = 0, unsigned const char mask=0xFF)
{
    fract_u copy;
    copy.dval = orig.dval;

    switch (level)
    {
    case 0:
        return copy;
    case 1:
        copy.data[0] &= ~(copy.data[0] & mask);
        copy.data[1] &= ~(copy.data[1] & mask);
        copy.data[2] &= ~(copy.data[2] & mask);
        return copy;
    case 2:
        copy.data[0] &= ~(copy.data[0] & mask);
        copy.data[1] &= ~(copy.data[1] & mask);
        return copy;
    case 3:
        copy.data[0] &= ~(copy.data[0] & mask);
        return copy;
    default:
        return copy;
    }
    return copy;
}


int main()
{
    std::map<float, int> sine_periods;
    std::map<float, int> cosine_periods;


    for(int i=0; i < LOOPSIZE; ++i)
    {
        fract_u t1 = {::sin((double)i)};
        fract_u t2 = preclevel2(t1, 1);
        sine_periods[t2.dval]++;
    }

    for(int i=0; i < LOOPSIZE; ++i)
    {
        fract_u t1 = {::sin((double)i)};
        fract_u t2 = preclevel2(t1, 1);
        cosine_periods[t2.dval]++;
    }


    for (auto it = sine_periods.begin(); it != sine_periods.end(); ++it)
    {
        std::cout << "[" << it->first << "][" << it->second << "]\r\n";
    }

    std::cout << "<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\r\n";

    for (auto it = cosine_periods.begin(); it != cosine_periods.end(); ++it)
    {
        std::cout << "[" << it->first << "][" << it->second << "]\r\n";
    }

    return 0;
}