[Wien] FFTW and ifx/icx issue relevant to WIEN2k

[Laurence Marks]

Comments.

   1. I have never seen -O3 do anything with icc/ifort except kill
   defenceless electrons and make the code *slower*. I will be happy to be
   proved wrong with ifx/icx.
   2. I *always* use -mkl, rather than making mistakes chasing how intel
   changes its libraries.
   3. I think you might have issues with -mkl_cdft (intel's version of
   fftw) and FFTW3


On Tue, Sep 9, 2025 at 4:10 PM Straus, Daniel B <dstraus at tulane.edu> wrote:

> Sorry for the long delay in responding—I was set to receive a digest of
> list messages, and it only comes once every couple of weeks.
>
>
>
> Yes, this is on a Zen 5 computer, and it is running Rocky Linux 10. I am
> using the Intel compiler and MKL, rather than the one AMD provides. IFX and
> ICX support the march=znver5 flag. All the WIEN2k 24.1 patches available as
> of 9/1 were installed.
>
>
>
> To be clear, on my workstation, FFTW still will work with WIEN2k even if
> the autoconf script is not regenerated, but there may be a performance
> impact as it is not using the proper Intel libraries for Fortran calls to
> FFTW. However, 3ddens would then not compile, and if I also attempted to
> use ELPA, then parallel LAPW1 would not compile. Regenerating the autoconf
> script for FFTW and recompiling it solved both problems. You should check
> the config.log for your FFTW compilation to see if there is a line such as
> “ld: cannot find -loopopt=0” to see if this error is occurring. For me, the
> configure script continued even after this error, but it was using GNU
> default libraries rather than the Intel provided libraries.
>
>
>
> siteconfig_lapw is set to use the ifx and icx compilers, and here are the
> flags under “Options” in siteconfig_lapw I am using the following compiler
> options for WIEN2k with the IFX compiler.
>
> Current settings:
>
>   M   OpenMP switch:           -qopenmp
>
>   O   Compiler options:        -O3 -march=znver5 -traceback -assume
> buffered_io -FR -I$(MKLROOT)/include
>
>   L   Linker Flags:            $(FOPT) -L$(MKLROOT)/lib -lpthread -lm -ldl
> -liomp5 -Wl,-rpath,$MKLROOT/lib
>
>   P   Preprocessor flags       '-DParallel'
>
>   R   R_LIBS (LAPACK+BLAS):    -lmkl_intel_lp64 -lmkl_intel_thread
> -lmkl_core
>
>   F   FFTW options:            -DFFTW3 -DFFTW_OMP
> -I/home/software/fftw-3.3.10/include
>
>       FFTW-LIBS:               -L/home/software/fftw-3.3.10/lib -lfftw3
> -lfftw3_omp
>
>   X   LIBX options:
>
>       LIBXC-LIBS:
>
>
>
> For Parallel Options in siteconfig_lapw, here are the flags I am using:
>
> Your current parallel settings (options and libraries) are:
>
>      C   Parallel Compiler:          mpiifx
>
>      FP  Parallel Compiler Options:  -O3 -FR -march=znver5 -fc=ifx
> -traceback -assume buffered_io -I$(MKLROOT)/include
>
>      MP  MPIRUN command:             mpirun -np _NP_ -machinefile _HOSTS_
> _EXEC_
>
>      O   Parallel OpenMP switch:     -qopenmp
>
>    Additional setting for SLURM batch systems (is set to 1 otherwise):
>
>      CN  Number of Cores:            1
>
>    Libraries:
>
>      Sp  SCALAPACK:                   -L$(MKLROOT)/lib
>
>                                                      -lmkl_scalapack_lp64
>
>                                                      -L$(MKLROOT)/lib
> -lmkl_blacs_intelmpi_lp64
>
>      E   ELPA options:                -DELPA
> -I/home/software/elpa-2025.06.001/include/elpa-2025.06.001/elpa
>
>
> -I/home/software/elpa-2025.06.001/include/elpa-2025.06.001/modules
>
>          ELPA-LIBS:                   -lelpa
> -L/home/software/elpa-2025.06.001/lib
> -Wl,-rpath=/home/software/elpa-2025.06.001/lib
>
>      RP  Parallel-Libs:      $(R_LIBS) -lmkl_cdft_core
>
>
>
> In case it’s relevant here is what I passed to the configure script for
> FFTW3 (after regenerating the script with autoconf):
>
> module load oneapi/2025.2.0
>
> ./configure --prefix=/home/software/fftw-3.3.10 CC="mpiicx -cc=icx"
> MPICC="mpiicx -cc=icx" F77="mpiifx -fc=ifx" FFLAGS="-O3 -march=znver5
> -I"${MKLROOT}/include"" CFLAGS="-O3 -march=znver5 -I"${MKLROOT}/include""
> CXXFLAGS="-I"${MKLROOT}/include"" LDFLAGS="-L${MKLROOT}/lib
> -lmkl_scalapack_lp64 -lmkl_cdft_core -lmkl_intel_lp64 -lmkl_intel_thread
> -lmkl_core -lmkl_blacs_intelmpi_lp64 -liomp5 -lpthread -lm -ldl"
> --enable-option-checking=fatal --enable-avx512 --enable-avx2 --enable-mpi
> --enable-openmp --enable-threads
>
>
>
> And for ELPA:
>
> module load oneapi/2025.2.0
>
> ./configure --prefix=/home/software/elpa-2025.06.001 CC="mpiicx -cc=icx"
> CXX="mpiicpx -cxx=icpx" FC="mpiifx -fc=ifx" CFLAGS="-O3 -march=znver5
> -I"${MKLROOT}/include"" FCFLAGS="-O3 -march=znver5 -I"${MKLROOT}/include""
> CXXFLAGS="-O3 -march=znver5 -I"${MKLROOT}/include""
> LDFLAGS="-L${MKLROOT}/lib -lmkl_scalapack_lp64 -lmkl_cdft_core
> -lmkl_intel_lp64 -lmkl_intel_thread -lmkl_core -lmkl_blacs_intelmpi_lp64
> -liomp5 -lpthread -lm -ldl" --enable-option-checking=fatal --with-mpi=yes
> --enable-openmp=yes
>
>
>
> Hopefully this is helpful.
>
>
>
>
>
>
>
> Daniel Straus
>
> Assistant Professor
>
> Department of Chemistry
>
> Tulane University
>
> 5088 Percival Stern Hall
>
> 6400 Freret Street
>
> New Orleans, LA 70118
>
> (504) 862-3585
>
> http://straus.tulane.edu/
>
>
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-- 
Emeritus Professor Laurence Marks (Laurie)
Northwestern University
Webpage <http://www.numis.northwestern.edu> and Google Scholar link
<http://scholar.google.com/citations?user=zmHhI9gAAAAJ&hl=en>
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Györgyi
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