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;
}
}