RFC: Discontinuing static-link library

rfcs/20250709-discontinuing-static-lib/README.md

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+# Discontinuing static-link library
+
+## Introduction
+
+When building oneDAL, it produces both shared libraries for dynamic linkage and
+static-link objects (`.a`/`.lib`).
+
+The produced builds are distributed through multiple channels, including PyPI,
+conda-forge, Intel's conda channel, Spack, NuGet, offline installers for Windows
+and Linux, and Intel repositories for Linux package managers like APT.
+
+Some of those distributions include only the shared library - for example, there
+are no static-link oneDAL libraries distributed in PyPI and NuGet due to file
+size constraints, nor in Spack.
+
+Most usage of oneDAL happens through the Python bindings with the Extension for
+Scikit-Learn, which only uses the shared library of oneDAL. Other known public
+consumers of oneDAL, such as
+[OAP MLlib](https://github.com/oap-project/oap-mllib) and
+[ML.net](https://www.nuget.org/packages/Microsoft.ML.OneDal/) also use the
+shared library, and do so in the way of creating another library with bindings
+for oneDAL that are exposed to final users in more convenient languages.
+
+We are not aware of any users of the static-link library of oneDAL, whether
+public or private, and it is unclear whether there are good use-cases for a
+static-link oneDAL library.
+
+Procedures from oneDAL are unlikely to be used as building blocks in a broader
+algorithm the way other libraries such as MKL would, and applications training
+or serving machine learning models for tabular data typically do so from
+interpreted languages like Python. Use-cases such as embedded devices, where
+usage of C++ for serving machine learning models might be more common, are
+unlikely to rely on algorithms for tabular data like the ones offered by oneDAL.
+
+Yet, the static library is bundled in many distribution channels even if it
+doesn't get used, increasing download sizes very significantly, and increasing
+compilation times during development due to required production of these files.
+
+## Proposal
+
+The proposal here is to not produce static-link files for oneDAL at all, and to
+discontinue the package `dal-static`.
+
+Being a large breaking change, this would need to be done in a major release
+such as 2026.0.
+
+## Open Questions
+
+* Do other UXL members rely on the static-link files?
+* Are there any known consumers of the static-link oneDAL library?
+* Would it be better to remove the static-link library altogether, or to leave
+  it as a non-default option? It might be hard to test it properly if not built
+  and distributed by default, but could be a reasonable compromise.