fractal-serial.cpp

#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>

#include "writeBMP.hpp"

#define xMin 0.74395
#define xMax 0.74973
#define yMin 0.11321
#define yMax 0.11899

int main(int argc, char *argv[])
{

  double dx, dy;
  int width;
  const int maxdepth = 256;
  struct timeval start, end;

  /* check command line */
  if(argc != 2) {fprintf(stderr, "usage: exe <width> \n"); exit(-1);}
  width = atoi(argv[1]);
  if (width < 10) {fprintf(stderr, "edge_length must be at least 10\n"); exit(-1);}

  dx = (xMax - xMin) / width;
  dy = (yMax - yMin) / width;

  printf("computing %d by %d fractal with a maximum depth of %d\n", width, width, maxdepth);

  unsigned char *cnt = (unsigned char*)malloc(width * width * sizeof(unsigned char));

  /* start time */
  gettimeofday(&start, NULL);

  for(int row = 0; row < width; ++row) {
    for(int col = 0; col < width; ++col) {

      double x2, y2, x, y, cx, cy;
      int depth;

      cy = yMin + row * dy; //compute row #
      cx = xMin + col * dx; //compute column #
      x = -cx;
      y = -cy;
      depth = maxdepth;
      do {
        x2 = x * x;
        y2 = y * y;
        y = 2 * x * y - cy;
        x = x2 - y2 - cx;
        depth--;
      } while ((depth > 0) && ((x2 + y2) <= 5.0));
      cnt[row * width + col] = depth & 255;

    }
  }

  /* end time */
  gettimeofday(&end, NULL);
  printf("compute time: %.8f s\n", end.tv_sec + end.tv_usec / 1000000.0 - start.tv_sec - start.tv_usec / 1000000.0);

  /* verify result by writing it to a file */
  if (width <= 2048) {
    WriteBMP(width, width, cnt, "fractal.bmp");
  }

  free(cnt);

  return 0;
}