When the function ifft(const vec &f, vec &t) is called with an input vector of size >= 256, the input vector is modified.
This bug occurs when the library FFTW3 is used.
--- begin code ---
int N = 256;
cvec tmp = f;
cvec d = tmp - f;
cout << d << endl;
--- end code ---
For N < 256 the vector 'd' is the zero vector as expected. However, for N >= 256 the first half of the vector 'd' is non-zero.