depending on intel-oneapi-runtime

[mabraham]

An app that compiles with %oneapi compilers ends up with a link-time dependency on intel_oneapi_runtime (of the same version as the compiler). This is useful because an app that requires(sycl) thereby gets its dependency on libsycl.so satisfied by intel_oneapi_runtime. If the same app also depends on parts of Intel's MKL library that depend on SYCL (eg. FFT) then spack ought to be able to choose a default version of intel_oneapi_mkl based on the version of the intel_oneapi_runtime. Typically exactly one runtime/compiler version is suitable for MKL, because libsycl.so increases SOVERSION with every compiler release and MKL must adapt to that. That is, there's a hard requirement for an app using aspects of MKL that require SYCL to use the versions of MKL and the compiler that shipped together.

If the user specified the compiler version but did not specify the MKL version, then there ought to be only one choice Spack can make, based on the common dependency of that runtime.

How should we express this in Spack? Any ideas? @rscohn2 FYI

[mabraham]

Using

    variant(
        "sycl",
        default=False,
        description="Use SYCL support - requires oneAPI SYCL runtime from matching compiler",
    )
    depends_on("intel-oneapi-runtime", when="+sycl")

in intel_oneapi_mkl/packages.py seems clear, but how do we then express that there's a 1:1 mapping between the version of the library and the version of the runtime?