Example #1
0
void down(int i)
{
    int vetsi, j;

    while(1){

       j = i << 1;
       if(j > sn) return;
       if(j+1 > sn) vetsi=1;
       else vetsi = isGE(j,j+1);

       if(vetsi) if isGE(i,j) return; else { swapx(j,i); i=j; }
       else if(isGE(i,j+1)) return; else { swapx(j+1,i); i=j+1; }
Example #2
0
void fft1x(Complex a[], int n, int iter, int flag)
{
	int i, it, j, j1, j2, k, xp, xp2;
	double arg, sign, w;
	Complex d1, d2, *p, *q, t, ww;

	if(n < 2)
	{
		fprintf(stderr, "Error : n < 2  in fft1()\n");
		return;
	}
	if(iter <= 0)
	{
		iter = 0;
		i = n;
		while((i /= 2) != 0)	iter++;
	}
	j = 1;
	for(i = 0; i < iter; i++)	j *= 2;
	if(n != j)
	{
		fprintf(stderr, "Error : n != 2 ^ k  in fft1()\n");
		return;
	}
	sign = (flag == 1)? 1.: -1.;
	xp2 = n;
	for(it = 0; it < iter; it++)
	{
		xp = xp2;
		xp2 = xp / 2;
		w = M_PI / xp2;
		for(k = 0; k < xp2; k++)
		{
			arg = k * w;
			ww = tocomplex(cos(arg), sign * sin(arg));
			i = k - xp;
			for(j = xp, p = a + i + xp, q = a + i + xp + xp2;
				j <= n; j += xp, p += xp, q += xp)
			{
				t = csub(*p, *q);
				*p = cadd(*p, *q);
				*q = cmul(t, ww);
			}
		}
	}
	j1 = n / 2;
	j2 = n - 1;
	j = 1;
	for(i = 1, p = a; i <= j2; i++, p++)
	{
		if(i < j)	swapx(p, a + j - 1);
		k = j1;
		while(k < j)
		{
			j -= k;
			k /= 2;
		}
		j += k;
	}
	if(flag == 0)	return;
	w = n;
	for(i = 0, p = a; i < n; i++, p++)	*p = cdiv1(*p, w);
	return;
}