Tetration fractal (C++)

tetration.cpp

#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cstdlib>
#include <cmath>

#ifdef _MSC_VER
inline double get_time()
{
    return static_cast<double>(std::clock()) / CLOCKS_PER_SEC;
}
#else
#include <sys/time.h>
inline double get_time()
{
    timeval tv;
    gettimeofday(&tv, 0);
    return tv.tv_sec + 1e-6 * tv.tv_usec;
}
#endif

using namespace std;

const double PI = 3.1415926535897931;

// left, top, width , height, screen width, screen height, max iterations, data[sw*sh]
void tetration(float l, float t, float w, float h, int sw, int sh, int mit, vector<int>& data)
{
    for (int ky = 0; ky < sh; ky++) {
        for (int kx = 0; kx < sw; kx++) {
            float x = l + w * kx / (sw - 1);
            float y = t + h * ky / (sh - 1);
            int i = 0;
            for (; i < mit - 1; i++) {
                float e = exp(-0.5 * PI * y);
                if (e != e) break;
                float p = PI * x * 0.5;
                x = e * cos(p);
                y = e * sin(p);
                if (x * x + y * y > 1e12) break;
            }
            data.push_back(i);
        }
    }
}

int main(int argc, char* argv[])
{
    if (argc < 6) {
        cerr << "Usage: " << argv[0] << " outfile left top width height [screen_width=512 screen_height=512 max_iters=256]" << endl;
        cerr << "  Ex. " << argv[0] << " tetration.out -1.5 0.0 0.75 0.75" << endl;
        exit(1);
    }

    fstream fs(argv[1], ios_base::out);
    float l = atof(argv[2]);
    float t = atof(argv[3]);
    float w = atof(argv[4]);
    float h = atof(argv[5]);

    int sw = 512;
    int sh = 512;
    int mit = 256;
    if (argc >= 7) sw = atoi(argv[6]);
    if (argc >= 8) sh = atoi(argv[7]);
    if (argc >= 9) mit = atoi(argv[8]);

    vector<int> data;

    cout << "Range: (" << l << ", " << t << ") - (" << l + w << ", " << t + h << ")" << endl;
    cout << "Image: " << sw << " x " << sh << endl;
    cout << "Max number of iterations: " << mit << endl;

    double start_time = get_time();
    tetration(l, t, w, h, sw, sh, mit, data);
    cout << "Time: " << get_time() - start_time << endl;

    int cnt = 0;
    fs << sw << " " << sh << endl;
    for (vector<int>::iterator p = data.begin(); p != data.end(); ++p, cnt++) {
        fs << *p << " ";
        if ((cnt + 1) % sw == 0) fs << endl;
    }

    return 0;
}

http://handasse.blogspot.com/2012/05/blog-post.html