FFTW vs Matlab FFT

Question

I posted this on matlab central but didn\'t get any responses so I figured I\'d repost here.

I recently wrote a simple routine in Matlab that uses an FFT in a for-l

Answer 1

I have found the following comment on the MathWorks website [1]:

Note on large powers of 2: For FFT dimensions that are powers of 2, between 2^14 and 2^22, MATLAB software uses special preloaded information in its internal database to optimize the FFT computation. No tuning is performed when the dimension of the FTT is a power of 2, unless you clear the database using the command fftw('wisdom', []).

Although it relates to powers of 2, it may hint upon that MATLAB employs its own 'special wisdom' when using FFTW for certain (large) array sizes. Consider: 2^16 = 65536.

[1] R2013b Documentation available from http://www.mathworks.de/de/help/matlab/ref/fftw.html (accessed on 29 Oct 2013)