Configuration fails with FFTW

[SimonRit]

Description

Configuring my ITK projection on Linux with ITK_USE_FFTWF and ITK_USE_FFTWD generates the following error since #5721:

CMake Error in Modules/Filtering/FFT/src/CMakeLists.txt:
  Target "ITKFFT" INTERFACE_LINK_DIRECTORIES property contains path:

    "/home/srit/src/itk/lin64/fftw/lib"

  which is prefixed in the build directory.

Steps to Reproduce

Clone ITK main and configure with cmake -DITK_USE_FFTWF=ON -DITK_USE_FFTWD=ON ITK_SOURCE_DIR

Reproducibility

100%

Versions

Environment

Ubuntu

[SimonRit]

Any suggestion @blowekamp?

[blowekamp]

I am looking into it. It looks like the issue does not occur with a system FFTW.

[SimonRit]

Yes, it doesn't occur with a system FFTW. Which I'm now using :-).

[blowekamp]

The issue seem to be:
set(ITKFFT_SYSTEM_LIBRARY_DIRS ${FFTW_LIBDIR})

This is likely not needed for the ITK build External Project of FFTW. There is a fair amount of which could be updated related to the FFT back ends. Here is a quick fix that seemed to work for me, in build and install.

diff --git a/CMake/itkExternal_FFTW.cmake b/CMake/itkExternal_FFTW.cmake
index 6369eaeeb9..e5c3693913 100644
--- a/CMake/itkExternal_FFTW.cmake
+++ b/CMake/itkExternal_FFTW.cmake
@@ -113,7 +113,6 @@ if(NOT ITK_USE_SYSTEM_FFTW)
${FFTW_STAGED_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}
)
set(FFTW_INCLUDE ${FFTW3_INCLUDE_DIRS})

• set(FFTW_LIBDIR ${FFTW3_LIBRARY_DIRS})
  set(
  ITK_FFTWF_LIBRARIES_NAMES
  fftw3f_threads
  @@ -173,7 +172,6 @@ if(NOT ITK_USE_SYSTEM_FFTW)
  )

  set(FFTW_INCLUDE ${FFTW3_INCLUDE_DIRS})

• set(FFTW_LIBDIR ${FFTW3_LIBRARY_DIRS})
  set(
  ITK_FFTWD_LIBRARIES_NAMES
  fftw3_threads

[SimonRit]

Works for me, thanks, but will this work for a system FFTW compiled in a non-system directory? should we remove it only if(NOT ITK_USE_SYSTEM_FFTW)?

[blowekamp]

The "build in" FFTW uses an ExternalProject to compile the FFTW library, and a manual installation of some files. This is not a robust/correct installation that can easily work with CMake targets/interfaces. Additionally, the ITK FFTW "option" also supports Intel's MKL, and an OpenCV FFTW library. These are all top level configurations. There a need to refactorthe FFTW options into a ThirdParty library with a ITK::ITKFFTWModule interface.

In the mean time a change like the following may mostly work the way the existing code did:
--- a/CMake/itkExternal_FFTW.cmake
+++ b/CMake/itkExternal_FFTW.cmake
@@ -110,7 +110,7 @@ if(NOT ITK_USE_SYSTEM_FFTW)
set(FFTW3f_INCLUDE_DIRS ${FFTW_STAGED_INSTALL_PREFIX}/include)
set(
FFTW3f_LIBRARY_DIRS

•  ${FFTW_STAGED_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}
  

•  $<BUILD_INTERFACE:${FFTW_STAGED_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}>
  

  )

However when ITK is installed it would not be correct, like the existing code.

[dzenanz]

Between @blowekamp and @SimonRit, is there enough appetite to do the proper refactoring? If not, backwards-equivalent fix from previous comment should be applied soon.

[blowekamp]

Between @blowekamp and @SimonRit, is there enough appetite to do the proper refactoring? If not, backwards-equivalent fix from previous comment should be applied soon.

Actually, removing the FFTW3f_LIBRARY_DIRS and changing to a full path for the libraries, with a generator expression for build, and install maybe closer and a better solution than suggested above.

There are still quite a few issue with the changes I'm trying to work through, so only quicker solution at the moment from me.

[SimonRit]

Between @blowekamp and @SimonRit, is there enough appetite to do the proper refactoring? If not, backwards-equivalent fix from previous comment should be applied soon.

Sorry I'll pass. I would need a proper training in modern CMake before being able to code something useful.

[dzenanz]

Brad, can you propose the PR with the quicker fix?