v5.1 of the Arnold core renderer has been released. A major update, 5.1 includes new sampling options, multiple denoisers, Toon shader, Alembic procedural, Profiling API, Operators, bug fixes & more.

https://www.solidangle.com/news/arnold-5-1/

https://support.solidangle.com/display/A5AFMUG/3.0.0

https://support.solidangle.com/display/A5AFMUG/Toon