topic intel fftw and opensource fftw in Intel® oneAPI Math Kernel Library

intel fftw and opensource fftw

psing51 — Fri, 03 Sep 2021 09:22:00 GMT

I am trying to compile a library which can enable fftw support by using following flag with ./configure script :
--with-fftw3=${FFTW_ROOT}

and i came across following statement here -

The FFTW3 wrappers provide a limited functionality compared to the original FFTW 3.x library, because of differences between FFTW and Intel® oneAPI Math Kernel Library FFT and TT functionality.

By "limited" , i assume that few functions may be missing in intel's fftw implementation.

Q1: Are there some recommendations to compile/link both intel fftw and the opensource implementation in such a way that the open source library (which i have compiled manually in my $HOME directory) should be used as fall back if the intel's fftw does not have the implementation for a particular function/routine - without creating symbol conflicts between common functions?

i.e.

in order to compile library , i plan to set and configure library as -
export CFLAGS="-I$MKLROOT/include/fftw"
export LDFLAGS="-L$MKLROOT/lib/intel64 -lfftw3xf_intel -lmkl_intel_lp64 -lmkl_sequential -lmkl_core -lfftw3_omp -lfftw3"

CC=icc ./configure --with-fftw3=${FFTW_ROOT}

I plan to setup FFTW_ROOT where FFTW_ROOT/lib will have following softlinks-
lib/libfftw3xc_intel.a lib/libfftw3xf_intel.a lib/libfftw3.so lib/libfftw3_omp.so
and FFTW_ROOT/include will point to $MKLROOT/include/fftw

i had compiled fftw3 wrappers as -
cd $MKLROOT
cd interfaces/fftw3xc
make libintel64 INSTALL_DIR=$MKLROOT/lib/intel64
cd $MKLROOT
cd interfaces/fftw3xf
make libintel64 INSTALL_DIR=$MKLROOT/lib/intel64
Q2: with aforementioned commands, i get 2 libraries - libfftw3xc_intel.a and libfftw3xf_intel.a
is there a way to get ".so"/dynamic version of these liraries?

Re: intel fftw and opensource fftw

VidyalathaB_Intel — Tue, 07 Sep 2021 06:51:27 GMT

Hi,

Thanks for reaching out to us.

>>i came across following statement here -

Could you please provide us the link from which you have taken the statement ?

Please refer the below link for more details on usage of intel's fftw3

https://software.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-c/top/appendix-c-fftw-interface-to-intel-math-kernel-library/fftw3-interface-to-intel-oneapi-math-kernel-library/using-fftw3-wrappers.html

>>Are there some recommendations to compile/link both intel fftw and the opensource implementation, in order to compile library

Did you face any issues while compiling the library by using only intel fftw?

The makefile from intel's fftw3 creates only .a files.

>>is there a way to get ".so"/dynamic version of these libraries?

You could try modifying the makefile to generate .so version of aforementioned libraries and see if it works.

Regards,

Vidya.

Re:intel fftw and opensource fftw

VidyalathaB_Intel — Tue, 14 Sep 2021 10:15:42 GMT

Hi,

Reminder:

Has the information provided helped? If yes, could you please confirm whether we can close this thread from our end?

Regards,

Vidya.

Re:intel fftw and opensource fftw

VidyalathaB_Intel — Tue, 21 Sep 2021 02:58:54 GMT

Hi,

We assume that your issue has been resolved. If you need any additional information from intel please post a new question as this thread will no longer be monitored.

Have a good day!

Regards,

Vidya.