"katz" <f_arikat@hotmail.com> wrote in message
news:qfCdnVdQhc4pn9XfRVn-pw@giganews.com...

> hello everyone,
> i just downloaded the FFTW library, and i read the tutorial (well..i
> skimmed through it).
>
> i'm using dev-C++. in c++, i constructed 2 vectors, and i have to convolve
> them using the FFTW library. the stuff in the tutorial seems much more
> complex than what i want to do, and i am a newbie. a really slow learning
> newbie that needs guidence. so, i was wondering if anyone could please
> point me in the right direction??
>
> i've searched through millions of websites, and i couldn't find what i was
> looking for. all i want really, is a very basic template of what code from
> the FFTW library looks like. i'm really really stuck. also, how shall i go
> about solving this problem of mine??
>
> i don't want to know the exact code, i would just like a template in
> english coz i really want to understand this first. any help given would
> be greatly appreciated.
>
> thank u in advance,
> katz
>

katz,
Forgive my criticism.... It seems to me that you're buried in code-ese and
not focusing on the *function* of the code. Different kinda template!
One can perform a circular convolution in the following way:
conv(a,b):
A=FFT(a)
B=FFT(b)
C=A*B
D=IFFT(c)=conv(a,b) (with the proper scaling of course)
Now, you do have to make sure that the lengths of the arrays is adequate.
If A is of length N
If B is of length M
Then the FFTs need to be at least of length M+N-1 which means you have to
zero pad a and b before the FFTs.
Then you may need to figure out the (circular) indices of arrays that make
sense for your application.
Fred

Reply by katz●March 28, 20052005-03-28

hello everyone,
i just downloaded the FFTW library, and i read the tutorial (well..i
skimmed through it).
i'm using dev-C++. in c++, i constructed 2 vectors, and i have to convolve
them using the FFTW library. the stuff in the tutorial seems much more
complex than what i want to do, and i am a newbie. a really slow learning
newbie that needs guidence. so, i was wondering if anyone could please
point me in the right direction??
i've searched through millions of websites, and i couldn't find what i was
looking for. all i want really, is a very basic template of what code from
the FFTW library looks like. i'm really really stuck. also, how shall i go
about solving this problem of mine??
i don't want to know the exact code, i would just like a template in
english coz i really want to understand this first. any help given would
be greatly appreciated.
thank u in advance,
katz
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