Java to D
Jeferson Andrade
geojaca at bol.com.br
Fri Jan 4 06:04:31 PST 2008
Hi,
I have this code in Java :
public static Complex[] fft(Complex[] x) {
int N = x.length;
System.out.println("-------------");
System.out.println(x.length);
// caso comum
if (N == 1) return new Complex[] { x[0] };
// radix 2 Cooley-Tukey FFT
if (N % 2 != 0) { throw new RuntimeException("N is not a power of 2"); }
// fft of even terms
Complex[] even = new Complex[N/2];
for (int k = 0; k < N/2; k++) {
even[k] = x[2*k];
}
Complex[] q = fft(even);
// fft of odd terms
Complex[] odd = even; // reuse the array
for (int k = 0; k < N/2; k++) {
odd[k] = x[2*k + 1];
}
Complex[] r = fft(odd);
// combine
Complex[] y = new Complex[N];
for (int k = 0; k < N/2; k++) {
double kth = -2 * k * Math.PI / N;
Complex wk = new Complex(Math.cos(kth), Math.sin(kth));
y[k] = q[k].plus(wk.times(r[k]));
y[k + N/2] = q[k].minus(wk.times(r[k]));
}
return y;
}
I changed Complex[] for creal[] and I made this code in D, but it contains error:
static creal[] fft(creal[] x)
{
int N = x.length;
writefln("-------------");
writefln(x.length);
// common case
if (N == 1) return new creal[] { x[0]; }; //the error is in this line
// radix 2 Cooley-Tukey FFT
if (N % 2 != 0) { throw new Exception("N nao e uma potencia de 2"); }
// fft of even terms
creal[] even = new creal[N/2];
for (int k = 0; k < N/2; k++) {
even[k] = x[2*k];
}
creal[] q = fft(even);
// fft of odd terms
creal[] odd = even; // reuse the array
for (int k = 0; k < N/2; k++) {
odd[k] = x[2*k + 1];
}
creal[] r = fft(odd);
// combine
creal[] y = new creal[N];
creal wk;
real wk1;
ireal wk2;
for (int k = 0; k < N/2; k++) {
real kth = -2 * k * PI / N;
//= new creal(Math.cos(kth), Math.sin(kth));
wk1 = cos(kth);
wk2 = cast(ireal) sin(kth);
wk = wk1 + wk2;
y[k] = q[k] + (wk * r[k]);
y[k + N/2] = q[k] - (wk * r[k]);
}
return y;
}
Somebody can gives a clue to me?
Thank you.
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