END OF AN ERA, FRACTALFORUMS.COM IS CONTINUED ON FRACTALFORUMS.ORG

  @SuppressWarnings("boxing")
  // n = number of points to dump out, s = scrambling value
  public static void quickHack(int n, int s)
  {
    // in C/C++ use unsigned
    int   si = s;
    float R = 1.f/n;
    float x,y;
    
    // hammersley style point set, sobel via graycode for second dimension
    for(int i=0; i<n; i++) {
      
      // the point S(i) = (x,y)
      x = i*R;
      /// with unsigned support lose the shift and multiply by 0x1p-32
      y = (si>>>8)*0x1p-24f;
      
      System.out.printf("%f %f\n",x, y);
      
      // update sobol value. GCC/VC have an intrinsic for trailing zeros
      // otherwise there's hacker's delight like methods
      si = si ^ 0x80000000 >>> Integer.numberOfTrailingZeros(~i);
    } 
    System.out.println();
  }

#include <stdint.h>

#ifdef __GNUC__
#define ctz(x) __builtin_ctz(x)
#else
// fill-in
#endif

// sequence state data (move this and function prototypes to a header)
typedef struct
{
  uint32_t i,d0,d1;
} Sobol2D_t;


// direction table
static uint32_t D[33];

// one-time initialization
void Sobol2D_Init()
{
  uint32_t c = D[0] = 1 << 31;
  
  for(int i=1; i<32; i++) {
    c = c ^ (c >> 1);
    D[i] = c;
  }
}

// reset the sequence
void Sobol2D_Reset(Sobol2D_t* data)
{
  data->i = data->d0 = data->d1 = 0;
}

// next value in the sequence
void Sobol2D_Next(float* v, Sobol2D_t* state)
{
  uint32_t c = ctz(~state->i);

  v[0] = state->d0 * 0x1p-32f;
  v[1] = state->d1 * 0x1p-32f;
  
  state->d0 ^= 0x80000000U >> c;
  state->d1 ^= D[c];
  state->i  += 1;    
}

void Sobol2D_Seek(Sobol2D_t* state, uint32_t num)
{
  uint32_t i = state->i;
  uint32_t n = i + num;
  uint32_t a = i ^ (i >> 1);
  uint32_t b = n ^ (n >> 1);
  uint32_t d = a ^ b;
  uint32_t c = 0;
  
  while(d != 0) {
    if ((d & 1) != 0) {
      d0 ^= 0x80000000 >> c;
      d1 ^= D[c];
    }
    d >>= 1;
    c  += 1;
  }
  state->i = n;
}

#if 1
#include <stdio.h>

void main(int argc, char** argv)
{
  Sobol2D_t d;
  float r[2];

  Sobol2D_Init();
  Sobol2D_Reset(&d);
  
  for(int i=0; i<22; i++) {
    Sobol2D_Next(r, &d);
    printf("%f %f\n", r[0],r[1]);
  }
}
#endif