Add ddc, fft, pdi and splines targets

[tpadioleau]

Current public targets:

• DDC::core contains the core part of DDC
• DDC::pdi and DDC::PDI_Wrapper (deprecated) contain the PDI extension
• DDC::fft contains the FFT extension
• DDC::splines contains the Splines extension
• DDC::DDC contains all

[tpadioleau]

Looks great

thanks!

[tpadioleau]

1. Should we internally use ddc_ or DDC:: targets ?

2. The NAMESPACE DDC:: option is almost then unused, only DDC::PDI_Wrapper and DDC::DDC take advantage of it. An alternative could be to use it for an impl namespace and keep an explicit management of the public namespace. For example:

   • in the CMakeLists.txt: install(EXPORT DDCTargets NAMESPACE DDC::Impl:: DESTINATION lib/cmake/DDC)
   • in the DDCConfig.cmake: add_library(DDC::core ALIAS DDC::Impl::ddc_core)

[jbigot]

1. Should we internally use ddc_ or DDC:: targets ?

   2. The NAMESPACE DDC:: option is almost then unused, only DDC::PDI_Wrapper and DDC::DDC take advantage of it. An alternative could be to use it for an impl namespace and keep an explicit management of the public namespace. For example:

      • in the CMakeLists.txt: install(EXPORT DDCTargets NAMESPACE DDC::Impl:: DESTINATION lib/cmake/DDC)
      • in the DDCConfig.cmake: add_library(DDC::core ALIAS DDC::Impl::ddc_core)

1. On my side, I use the following policy:

• use the non-namespaced, private target (ddc_*) when creating them
• use the namespaced, public target (DDC::*) when using them

so you'd have for example:

target_link_libraries(ddc_fft INTERFACE DDC::core Kokkos::kokkos KokkosFFT::fft)

ddc_fft, but DDC::core

2. DDC::Impl::ddc_* instead of DDC::ddc_* sounds like a good idea indeed, maybe makes it clearer that this is a private identifier.