Re: [Discuss-gnuradio] OFDM IFFT calculate

Hi SangHyuk

On 30.05.2016 14:25, SangHyuk Kim wrote:

Hi all,

The file, /gr-fft/lib/fft_vcc_fftw.cc(http://goo.gl/X8WNPh),

No need to use URL shorteners in Emails.
Why are you using a revision of that file from 2012? That is not what you should do. Select "branch: Master" from the drop-down menu; you should be looking at
http://gnuradio.org/redmine/projects/gnuradio/repository/entry/gr-fft/lib/fft_vcc_fftw.cc?rev=master .
Reading versions of code that no-one uses anymore doesn't help you !

> I can understand how get inputs to 'd_fft', but I don't know about d_fft->execute() that compute the fft.

So, here's how you approach something like this: Find out what "d_fft" is. For that, you often need to look in the .h file to your .cc.

There you'll find out which class type d_fft has.

Find that type's definition.

Or, you could just go to

and search for "execute" in the search box. That'll tell you the classes that have a method called "execute", and you can access the documentation to these.

I can't find its' implementation in anywhere so that I can't understand what happen in this function.

A DFT is performed, by calling the fftwf_execute function of the FFTw library, which really, just executes a fast DFT.


Best regards,
Marcus