Avoid downloading MKL artifact as FFTW dependency

Vasily_Pisarev · December 26, 2023, 11:58am

I am developing a package that uses FFTW.
Changing Manifest.toml by adding or removing packages triggers precompilation of all dependencies, during which MKL_jll downloads MKL binary.
BUT MKL in my case is only an optional dependence of FFTW and is not supposed to be used in my package.
Is there a way to skip artifact downloading on precompile?

giordano · December 26, 2023, 12:27pm

MKL_jll is loaded only if using MKL as provider explicitly:

github.com

JuliaMath/FFTW.jl/blob/7acdc2b8a6d4777bc73832b9afd55890bf9e2b9a/src/providers.jl#L83-L89


      
          # If we're using MKL, load it in and set library paths appropriately.
          @static if fftw_provider == "mkl"
              import MKL_jll
              libfftw3[] = MKL_jll.libmkl_rt_path
              libfftw3f[] = MKL_jll.libmkl_rt_path
              const _last_num_threads = Ref(Cint(1))
          end

So the artifact shouldn’t be loaded unless you’re asking for it.

Vasily_Pisarev · December 26, 2023, 2:15pm

IIUC, Pkg.precompile() precompiles everything in Manifest, and the artifact is downloaded at that stage.
I’ve found that disabling automatic precompilation at Manifest change seems to solve that issue locally, but more generally it’s weird that everyone getting my package also has to download MKL unless they set a specific environment variable.