Lyapunov Exponent (Processing)

LyapunovExponent.pde

/** Lyapunov Exponent
 * 
 * Based on code on pg. 62 of _Chaos in Wonderland_
 * by Clifford A. Pickover
 * 
 */

float calcLyapunovExponent(float a, float b, float c, float d) {
  float Lsum = 0;
  float n = 0;
  float x = 0.1;
  float y = 0.1;
  float  xe = x + 0.000001;
  float ye = y;
  float xx, yy, xsave, ysave, dLx, dLy, dL2, df, rs, L = 0;
  float bigNumber = 2139095039; /* Pickover's algorithm calls 
     for a long int (1000000000000) here, but I often get NaN returned 
     when using it in Processing, and I have found that using a 
     large float returns a value close enough to Pickover's to 
     be useful. */
    
  for(int i=0; i<10000000; i++) {
    xx = sin(y*b) + c*sin(x*b); yy = sin(x*a) + d*sin(y*a);
    xsave = xx; ysave = yy; x = xe; y = ye; n++;
    xx = sin(y*b) + c*sin(x*b); yy = sin(x*a) + d*sin(y*a);
    dLx = xx - xsave; dLy = yy - ysave; dL2 = dLx*dLx + dLy*dLy;
    df = bigNumber*dL2; rs = 1/sqrt(df);
    xe = xsave + rs*(xx - xsave); ye = ysave + rs*(yy - ysave);
    xx = xsave; yy = ysave; Lsum = Lsum + log(df); L = 0.721347*Lsum/n;
    x = xx; y = yy;
  }
  return L;
}