> Mark and others:
>
> I'm trying to get the KISS FFT working for me, but am struggling a little
> with the Real to Complex and back case. I suspect I'm misusing it somehow, I
> based this off the tests. The Complex to Complex fwd and inv (Full Spectrum)
> are working with similar logic.
>
> The forward operation seems to be accurate, but how do I do the inverse on
> 1/2 spectrum. If I don't remove the flag, I get a lot of errors at runtime
> (compiles fine):
>
> g++ on 64 bit linux
> *** glibc detected *** ./min: free(): invalid next size (normal):
> 0x0000000000da6790 ***
> ======= Backtrace: =========
> /lib/libc.so.6[0x7fc8a700cdd6]
> /lib/libc.so.6(cfree+0x6c)[0x7fc8a701174c]
>
> If I do remove the flag, thinking that maybe since the buffer is double, it
> will know it is a complex to real transform, but the answer is wrong.
>
> If a do a full spectrum all is happy.
>
> What am I doing wrong? If possible I'd like to just use the 1/2 spectrum.
> Thanks for any insight, really glad to have this out of the box like this.
>
> #include "Eigen/Core"
> #include "unsupported/Eigen/FFT"
> #include <complex>
>
> typedef std::complex<double> Complex;
>
> using namespace Eigen;
> using namespace std;
>
> int main() {
>
> FFT<double> fft;
> double dt(1e-3);
>
> VectorXd timeseries(200);
> VectorXcd fd(200);
>
> for (int i=0; i<200; ++i) {
> timeseries[i] = std::sin((double)(i)*dt*95.);
> }
>
> fft.SetFlag(fft.HalfSpectrum );
> fft.fwd(fd, timeseries);
> VectorXd out;
>
> // faults if I don't remove, wrong answer if I do
> fft.ClearFlag(fft.HalfSpectrum );
> fft.inv(out, fd);
>
> for (int i=0; i< out.size(); ++i) {
> cout << timeseries[i] << "\t" << out[i] << endl;
> }
> }
>