mlpack 4: a fast, header-only C++ machine learning library

For over 15 years, the mlpack machine learning library has served as a "swiss army knife" for C++-based learning. Its efficient implementations of common and cutting-edge algorithms have been used in wide variety scientific industrial applications. This paper overviews 4, significant upgrade its predecessor. The significantly refactored redesigned to facilitate an easier prototyping-to-deployment pipeline, including bindings other languages (Python, Julia, R, Go, command line) that allow prototyping be seamlessly performed environments than C++. is open-source software, distributed under permissive 3-clause BSD license; it can obtained at https://mlpack.org