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Author: FatemehFatemeh Date: Jul 5, 2008 02:24
Dear all;
I'm going to use rlft3.f (3D Fast Fourier transform subroutine in
Numerical Recipes book )
I have constructed a 107*107*107 mesh for data.
I should call rlft3(data,speg,nn1,nn2,nn3,isign).
-----------------------------------------------------------------------------
SUBROUTINE rlft3(data,speq,nn1,nn2,nn3,isign)
INTEGER isign,nn1,nn2,nn3
COMPLEX data(nn1/2,nn2,nn3),speq(nn2,nn3)
-----------------------------------------------------------------------------
1- I don't understand why for data is written nn1/2 ? I have a
107*107*107 mesh!!!
2- Is it true to put nn1=nn2=nn3=107
3- I don't know what should I put instead of speq ?
I'm anxiously looking forward your reply and guidlines.
With my best regards,
Fatemeh
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Author: dominiqdominiq Date: Jul 5, 2008 02:41
On 5 juil, 11:24, Fatemeh gmail.com> wrote:> Dear all;
>
> I'm going to use rlft3.f (3D Fast Fourier transform subroutine in
> Numerical Recipes book )
> I have constructed a 107*107*107 mesh for data.
> I should call rlft3(data,speg,nn1,nn2,nn3,isign).
> --------------------------------------------------------------------------- --
> SUBROUTINE rlft3(data,speq,nn1,nn2,nn3,isign)
> INTEGER isign,nn1,nn2,nn3
> COMPLEX data(nn1/2,nn2,nn3),speq(nn2,nn3)
> --------------------------------------------------------------------------- --
> 1- I don't understand why for data is written nn1/2 ? I have a
> 107*107*107 mesh!!!
> 2- Is it true to put nn1=nn2=nn3=107
> 3- I don't know what should I put instead of speq ?
>
> I'm anxiously looking forward your reply and guidlines.
> With my best regards,
> Fatemeh ...
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Author: FatemehFatemeh Date: Jul 5, 2008 03:36
On Jul 5, 1:41 pm, dominiq wrote:
> On 5 juil, 11:24, Fatemeh gmail.com> wrote:
>
>
>>> Dear all;
>
>> I'm going to use rlft3.f (3D Fast Fourier transform subroutine in
>> Numerical Recipes book )
>> I have constructed a 107*107*107 mesh for data.
>> I should call rlft3(data,speg,nn1,nn2,nn3,isign).
>> --------------------------------------------------------------------------- --
>> SUBROUTINE rlft3(data,speq,nn1,nn2,nn3,isign)
>> INTEGER isign,nn1,nn2,nn3
>> COMPLEX data(nn1/2,nn2,nn3),speq(nn2,nn3)
>> --------------------------------------------------------------------------- --
>> 1- I don't understand why for data is written nn1/2 ? I have a
>> 107*107*107 mesh!!!
>> 2- Is it true to put nn1=nn2=nn3=107
>> 3- I don't know what should I put instead of speq ? ...
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Author: dominiqdominiq Date: Jul 5, 2008 05:00
On 5 juil, 12:36, Fatemeh gmail.com> wrote:> On Jul 5, 1:41 pm, dominiq wrote:
>
>> On 5 juil, 11:24, Fatemeh gmail.com> wrote:>
>>> Dear all;
>
>>> I'm going to use rlft3.f (3D Fast Fourier transform subroutine in
>>> Numerical Recipes book )
>>> I have constructed a 107*107*107 mesh for data.
>>> I should call rlft3(data,speg,nn1,nn2,nn3,isign).
>>> --------------------------------------------------------------------------- --
>>> SUBROUTINE rlft3(data,speq,nn1,nn2,nn3,isign)
>>> INTEGER isign,nn1,nn2,nn3
>>> COMPLEX data(nn1/2,nn2,nn3),speq(nn2,nn3)
>>> --------------------------------------------------------------------------- --
>>> 1- I don't understand why for data is written nn1/2 ? I have a
>>> 107*107*107 mesh!!!
>>> 2- Is it true to put nn1=nn2=nn3=107
>>> 3- I don't know what should I put instead of speq ? ...
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Author: James Van BuskirkJames Van Buskirk Date: Jul 5, 2008 07:38
> The basic FFT requires sizes that are powers of 2. Some packages
> extend that to powers of small primes (typically 3 and 5), but I don't
> think this is the case for Numerical Recipes. Nevertheless 107 is a
> prime and is unlikely to be accepted in any FFT package.
107 is kind of ugly because (107-1)/2 = 53 which I do in fact have an
FFT for:
http://home.comcast.net/~kmbtib/codelets.ZIP
but 53 is rather ugly in itself. For some of these primes it gets
more efficient to use the chirp-z method rather than Rader's method,
but you can do an FFT of any order if you really have to.
--
write(*,*) transfer((/17.392111325966148d0,6.5794487871554595D-85, &
6.0134700243160014d-154/),(/'x'/)); end
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