matlab compatible ifft
y = tftb_ifft(x, n)
This funcion is much (100x) faster then mtlb_ifft
Compute the IFFT of A using subroutines from FFTW. The IFFT is calculated along the first non-singleton dimension of the array. Thus if A is a matrix, `ifft (A)' computes the IFFT for each column of A.
If called with two arguments, N is expected to be an integer specifying the number of elements of A to use, or an empty matrix to specify that its value should be ignored. If N is larger than the dimension along which the FFT is calculated, then A is resized and padded with zeros. Otherwise, if N is smaller than the dimension along which the IFFT is calculated, then A is truncated.