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..
.. Licensed under the Apache License, Version 2.0 (the "License");
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..     http://www.apache.org/licenses/LICENSE-2.0
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.. include:: substitutions.rst

=====================
About the |sklearnex|
=====================

The |sklearnex| is a free and open-source software accelerator built atop of the |sklearn| and the :external+onedal:doc:`oneDAL <index>` (|onedal|) libraries.

It mostly works by replacing selected calls to algorithms in |sklearn| with calls to the |onedal| library, which offers more optimized versions of the same routines (see :doc:`algorithms`). The optimizations in the |onedal| in turn are achieved by leveraging SIMD instructions and exploiting cache structures of modern hardware, along with using the `oneMKL <https://www.intel.com/content/www/us/en/developer/tools/oneapi/onemkl.html>`__ library for linear algebra operations in place of the `OpenBLAS <https://www.openmathlib.org/OpenBLAS/>`__ library used by default by |sklearn|.

Unlike other libraries in the Python ecosystem, classes and functions in the |sklearnex| are not just :external+sklearn:doc:`scikit-learn-compatible <developers/develop>`, but rather are built atop of |sklearn| itself by inheriting from their classes directly, defining the same attributes that the stock version of |sklearn| would do for each estimator, and reusing most of scikit-learn's estimator methods where appropriate.

The |sklearnex| is regularly tested for API compatibility and for correctness against |sklearn|'s own test suite (see :ref:`conformance_tests` for more information), and can be easily swapped in place of the stock |sklearn| library by :doc:`patching <patching>` it.

The |sklearnex| aims to be compatible with the last 3 minor releases of |sklearnex| available at any given time, in addition to the 1.0 release as a special case, and ensures this compatibility by offering different code routes according to the |sklearn| version encountered at runtime - for example, if a given attribute of a class is removed in version 1.x of |sklearn|, the |sklearnex| will not set that attribute when running with |sklearn| >=1.x, but will still do so when running with |sklearn| <1.x, in order to guarantee full API compatibility.

Performance of the |sklearnex| is regularly measured and compared against that of other libraries using public and synthetic datasets through `sklbench <https://github.com/IntelPython/scikit-learn_bench>`__, which is also free and fully open-source.

Initially developed by Intel as the Intel Extension for Scikit-learn*, the |sklearnex| and the |onedal| are now projects under the `UXL Foundation <https://uxlfoundation.org>`__ umbrella, and can be built from source to provide accelerated routines for other platforms such as ARM and RISCV - see :doc:`building-from-source` for more information.