The problem lies in the Complex.h, as you indicated.  Apparently, I had a
local "Complex.h" that I was including (used company-wide) as opposed to
the widely accepted standard C-version, <complex.h>.  Thanks again for
your help.

-Mark

>If you #include <complex.h> (*not* <Complex.h>, whatever that is)
>before fftw.h, *and* your compiler is C99-compliant (at least as far as
>complex types go), then fftw_complex is the same thing as C99's "double
>complex" type, as described in the manual.
>
>If you are using some non-C99 complex data type or your compiler is not
>C99-compliant, then this will not work.  However, if your complex data
>type consists of the real part followed by the imaginary part (e.g.
>struct { double real, imag; }) then it should be bit compatible with
>fftw_complex and you can just typecast your array pointer when passing
>to FFTW.
>
>Steven
>
>


		
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If you #include <complex.h> (*not* <Complex.h>, whatever that is)
before fftw.h, *and* your compiler is C99-compliant (at least as far as
complex types go), then fftw_complex is the same thing as C99's "double
complex" type, as described in the manual.

If you are using some non-C99 complex data type or your compiler is not
C99-compliant, then this will not work.  However, if your complex data
type consists of the real part followed by the imaginary part (e.g.
struct { double real, imag; }) then it should be bit compatible with
fftw_complex and you can just typecast your array pointer when passing
to FFTW.

Steven

>Data[j][0] is the real part and Data[j][1] is the imaginary part; what
>else is there to understand?  Surely you can write a loop yourself?
>
>Regarding typecasts, it depends on what "complex" type you are talking
>about.  Conversion from both the C99 complex types and the C++ complex
>types are described in the reference section of the FFTW manual.
>
>It sounds like you are having basic problems with the C language, and
>comp.lang.c might be a more appropriate forum (or comp.lang.c++ if you
>are using C++).
>
>Cordially,
>Steven G. Johnson
>

For the record, this is in C.  Also, I completely understand the data type
(e.g.-Data[j][0],Data[j][1]...) fftw_complex has.  The manual makes it seem
as if you don't *need* to put it in that type, however.  As long as you put
your #include <Complex.h> before the #include <fftw3.h>.  A simple for loop
is easy, yes.  However, it is also inefficient.  If the fftw supports
"complex" data types, I would like to take advantage of not having to run
a loop every time to cast it into fftw_complex data.  However, if it is
not supported, in fact, then I'll have to do it the old fashion way.  

I appreciate your help, Steven.  Maybe my questions are too vague and/or
you are receiving them wrong.  I don't think the problem is a comfort
level with the C language by any means.

Regards,

Mark

		
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mdholmes wrote:
> When I attempt to execute the plan with "complex" data, I get a compile
> error.  However, when I execute on "complex" data cast into "fftw_complex"
> within the plan call, it compiles and runs.  Unfortunately, it does not
> cast the complex data into equivalent "fftw_complex" data.  Do you have to
> go term by term (for loop) and put the data in Data[j][0] for real and
> Data[j][1] for imaginary manually?  Or is there a way to either execute
> the plan on "complex" data and/or effectively cast "complex" data to
> "fftw_complex"?  Thanks again.

Data[j][0] is the real part and Data[j][1] is the imaginary part; what
else is there to understand?  Surely you can write a loop yourself?

Regarding typecasts, it depends on what "complex" type you are talking
about.  Conversion from both the C99 complex types and the C++ complex
types are described in the reference section of the FFTW manual.

It sounds like you are having basic problems with the C language, and
comp.lang.c might be a more appropriate forum (or comp.lang.c++ if you
are using C++).

Cordially,
Steven G. Johnson

I have the manual and have read the related chapters; however, there seems
to be some ambiguity in what values the variables should take on.  I
appreciate the help, though.  Using values reflected in your response did
not prove any better in running the planner.  I believe the problem is in
the casting of the data.

When I attempt to execute the plan with "complex" data, I get a compile
error.  However, when I execute on "complex" data cast into "fftw_complex"
within the plan call, it compiles and runs.  Unfortunately, it does not
cast the complex data into equivalent "fftw_complex" data.  Do you have to
go term by term (for loop) and put the data in Data[j][0] for real and
Data[j][1] for imaginary manually?  Or is there a way to either execute
the plan on "complex" data and/or effectively cast "complex" data to
"fftw_complex"?  Thanks again.

-Mark

>n[0] = N
>howmany=M
>idist=N
>istride=1
>inembed = onembed = NULL
>
>Assuming you use the same layout for the output, odist=idist and
>ostride=istride.
>
>Cordially,
>Steven G. Johnson
>
>PS. You know, all of these parameters *are* documented in the manual.
>
>


		
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mdholmes wrote:
> I am using FFTW 3.0.1 with a C-program I'm developing.  My input data
> consists of a block of complex data for M channels ordered in the
> following fashion:
>
> input = [ chan1_sample0, chan1_sample1,...,chan1_sampleN-1,
> chan2_sample0,...,chan2_sampleN-1,...,...,chanM_sample0,...,chanM_sampleN-1]
>
> I would like to take advantage of the "Advanced Complex DFT" capability
> (e.g.-fftw_plan_many_dft()) to avoid having to call the routine for every
> FFT-size for each channel.  If I wanted to take an LF-size fft of the
> input for each channel, how do I set my arguments accordingly given the
> abovementioned input layout?  In particular, I am confused what to make my
> "const int *n", "int howmany", "const int *{i,o}nembed", "{i,o}stride",
> "{i,o}dist", etc.  Thanks in advance.

n[0] = N
howmany=M
idist=N
istride=1
inembed = onembed = NULL

Assuming you use the same layout for the output, odist=idist and
ostride=istride.

Cordially,
Steven G. Johnson

PS. You know, all of these parameters *are* documented in the manual.

I am using FFTW 3.0.1 with a C-program I'm developing.  My input data
consists of a block of complex data for M channels ordered in the
following fashion:

input = [ chan1_sample0, chan1_sample1,...,chan1_sampleN-1,
chan2_sample0,...,chan2_sampleN-1,...,...,chanM_sample0,...,chanM_sampleN-1]

I would like to take advantage of the "Advanced Complex DFT" capability
(e.g.-fftw_plan_many_dft()) to avoid having to call the routine for every
FFT-size for each channel.  If I wanted to take an LF-size fft of the
input for each channel, how do I set my arguments accordingly given the
abovementioned input layout?  In particular, I am confused what to make my
"const int *n", "int howmany", "const int *{i,o}nembed", "{i,o}stride",
"{i,o}dist", etc.  Thanks in advance.

Regards,

Mark


		
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