For those involved in high-performance computing (HPC) and computational science and engineering (CSE), Gentoo, is a powerful tool, both on the desktop and on servers or clusters. With it, users can build environments that do not waste time offering unwanted network services and system daemons, and the binaries for the OS can be highly optimized to take full advantage of the system architecture. In particular, this can improve the efficiency of numerical simulations that depend on floating point performance. Shaving 1 or 2 cycles from an operation may not seem like much, but when the routine is executed 5 million times per calculation, the savings rapidly add up. Also, Gentoo doesn't have a rigid release cycle with EOL dates forced on users who have working systems. Administrators and users have the ultimate control over when upgrades are made and to which packages. Finally, a group of enthusiastic volunteers have written ebuilds for over 100 different scientific and engineering applications and libraries, making them readily accessible to the user community.Computational Science and Engineering is related to but distinct from Computer Science. It is not usually concerned with research into computing for its own ends, but as a tool for making advances in other fields. It covers areas as broad as Geographic Information Systems, Bioinformatics, Computational Fluid Dynamics, Spectrum Analysis and Chemical Reactor Design.