private static DoubleLargeArray myFFT(DoubleLargeArray input) {
DoubleFFT_1D fftDo = new DoubleFFT_1D(input.length());
DoubleLargeArray fft = new DoubleLargeArray(input.length() * 2);
for (long k = 0; k < input.length(); k++) {
fft.setDouble(k, input.getDouble(k));
}
fftDo.realForwardFull(fft);
return fft;
}
private static DoubleLargeArray xcorr(DoubleLargeArray x1, DoubleLargeArray x2) {
double tmp = 0;
for (long k = 0; k < x2.length() / 2; k++) {
tmp = x2.getDouble(k);
x2.setDouble(k, x2.getDouble(x2.length() - 1 - k));
x2.setDouble(x2.length() - 1 - k, tmp);
}
DoubleLargeArray corr = conv(x1, x2);
return corr;
}
private static DoubleLargeArray conv(DoubleLargeArray x1, DoubleLargeArray x2) {
long fftsize = x1.length() + x2.length() - 1;
DoubleLargeArray newx1 = new DoubleLargeArray(fftsize);
DoubleLargeArray newx2 = new DoubleLargeArray(fftsize);
for (long k = 0; k < fftsize; k++) {
double val = k >= x1.length() ? 0 : x1.getDouble(k);
newx1.setDouble(k, val);
val = k >= x2.length() ? 0 : x2.getDouble(k);
newx2.setDouble(k, val);
}
DoubleLargeArray fft1 = myFFT(newx1);
DoubleLargeArray fft2 = myFFT(newx2);
for (long i = 0; i < fftsize; i++) {
double[] tmpResult =
complexMultiply(
fft1.getDouble(i * 2),
fft1.getDouble(i * 2 + 1),
fft2.getDouble(i * 2),
fft2.getDouble(i * 2 + 1));
fft1.setDouble(2 * i, tmpResult[0]);
fft1.setDouble(2 * i + 1, tmpResult[1]);
}
DoubleLargeArray fullConv = myIFFT(fft1);
DoubleLargeArray validConv = new DoubleLargeArray(fullConv.length() / 2 - 2 * x2.length() + 2);
for (long k = 0; k < validConv.length(); k++) {
validConv.set(k, fullConv.getDouble((k + x2.length() - 1) * 2));
}
return validConv;
}
public static long singalShift(double[] x1, double[] x2) {
DoubleLargeArray a = new DoubleLargeArray(x1);
DoubleLargeArray b = new DoubleLargeArray(x2);
DoubleLargeArray c = null;
c = xcorr(a, b);
long idx = 0;
double val = c.getDouble(idx);
for (long k = 0; k < c.length(); k++) {
if (c.getDouble(k) > val) {
idx = k;
val = c.getDouble(k);
}
}
return idx;
}
private static DoubleLargeArray myIFFT(DoubleLargeArray input) {
DoubleFFT_1D ifftDo = new DoubleFFT_1D(input.length() / 2);
ifftDo.complexInverse(input, true);
return input;
}