topic Re: Using FFTW Wrapper - fftw_plan_many_dft in Intel® oneAPI Math Kernel Library

Using FFTW Wrapper - fftw_plan_many_dft

mckinlk — Tue, 07 Jul 2009 17:38:39 GMT

I was hoping someone could shed some light...

I have inherited an application which originally uses FFTW and has been compiled to work with MKL.

There are calls to fftw_plan_many_dft, and I am having difficultly on what is actually being calculated.

The call is the following:

fftw_plan_many_dft(rank, *n, howmany, inembed, istride, idist, onembed, ostride, odist, sign)

rank = 1 (1D FFT)
*n = n[0] = 4096
howmany = 64
inembed = onembed = NULL (default to n[0])
istride = ostride = 64
idist = odist = 1
sign = 1 or -1 (INVERSE or FORWARD)

What confuses me is the stride != 1, any help would be greatly appreciated.

Re: Using FFTW Wrapper - fftw_plan_many_dft

Kazik — Wed, 08 Jul 2009 10:16:36 GMT

Hi mckinlk,
unfortunately I cannot answer your question but maybe you could help me.
I'm also struggling with the FFTW wrapper library. Please, tell me is there any specific way you link your program? Or do you include some specific libraries (apart from #include "fftw3.h" directly in your code of course)? Or is it only
icpc Project.cpp -lfftw3
?
I would be very grateful for any comments. Now, I'm not sure if the "installation" of the wrapper library went wrong or is there some other reason (using standard g++ compiler with "pure" FFTW everything works perfect).
Thank you and I'm sorry I cannot help you.
--
Kind regards,
Kazik

Re: Using FFTW Wrapper - fftw_plan_many_dft

mckinlk — Wed, 08 Jul 2009 12:40:37 GMT

Quoting - Kazik

When I compile for MKL, I have the following in my Makefile

LIB_DIRS += -L/opt/intel/mkl/$(MKL_VER)/lib/$(MKL_ARCH)
INC_DIRS += -I/opt/intel/mkl/$(MKL_VER)/include
INC_DIRS += -I/opt/intel/mkl/$(MKL_VER)/include/fftw
LIB_FILES += -lpthread -lfftw3xc_intel -lmkl -lm

My include remains as #include but due to the new directory paths, it gets pointed to the Intel wrapper header.

Re: Using FFTW Wrapper - fftw_plan_many_dft

Kazik — Wed, 08 Jul 2009 14:36:26 GMT

Quoting - mckinlk

Thank you man,
I have nearly the same makefile. The only difference is that I have
LIB_FILES += -lfftw3 -lmkl -lm
but even when I've change into -lfftw3xc_intel, still didn't work. I have something like this:
-------------------------------------------------------------------------------------------------
icpc -m64 -O3 -openmp -parallel FFT.cpp -L/local/intel/Compiler/11.0/081/mkl/lib/em64t -I. -I/local/intel/Compiler
/11.0/081/mkl/include -I/local/intel/Compiler/11.0/081/mkl/include/fftw -lfftw3xc_intel -lmkl -lm

FFT.cpp(32): error: identifier "FFTW_IN_PLACE" is undefined
p=fftw_create_plan(M, FFTW_FORWARD, FFTW_MEASURE | FFTW_IN_PLACE | FFTW_USE_WISDOM);
^
FFT.cpp(32): error: identifier "FFTW_USE_WISDOM" is undefined
p=fftw_create_plan(M, FFTW_FORWARD, FFTW_MEASURE | FFTW_IN_PLACE | FFTW_USE_WISDOM);
^
FFT.cpp(32): error: identifier "fftw_create_plan" is undefined
p=fftw_create_plan(M, FFTW_FORWARD, FFTW_MEASURE | FFTW_IN_PLACE | FFTW_USE_WISDOM);
^
FFT.cpp(46): error: expression must have class type
in.re = real(fu_in);
^
FFT.cpp(47): error: expression must have class type
in.im = imag(fu_in);
^
FFT.cpp(49): error: identifier "fftw_one" is undefined
fftw_one(pl_forward, in, out);
^
FFT.cpp(53): error: expression must have class type
out_re_robo = out.re;
^
FFT.cpp(54): error: expression must have class type
out_im_robo = out.im;
^
compilation aborted for FFT.cpp (code 2)
make: *** [FFT] Error 2
-------------------------------------------------------------------------------------------------

Thank you for your help.
Still, any ideas would be greatly appreciated.
--
Kind regards,
Kazik

Re: Using FFTW Wrapper - fftw_plan_many_dft

mckinlk — Wed, 08 Jul 2009 18:45:47 GMT

Quoting - Kazik

You might want to ensure the version of FFTW you started out with is compatible with the MKL wrapper, you seem to have several function prototypes that I do not see in my fftw3.h

I am using fftw-3.1.2 and MKL version 10.1.1.019

Re: Using FFTW Wrapper - fftw_plan_many_dft

Kazik — Tue, 14 Jul 2009 18:03:40 GMT

Quoting - mckinlk

Thank you,
that was the crucial hint. Indeed, I was using in my code some FFTW1 functions (I thought they will be automatically supported by the FFTW3) and tried to compile with FFTW3 library.. No comment about that.. Anyway, now it's working perfectly. Thanks once more.
--
Kind regards,
Kazik