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Environment Modules Using Lmod

Environment Control

Article from ADMIN 47/2018

By Jeff Layton

The indispensable Lmod high-performance computing tool allows users to control their build and execution environment.

One of the key tools for any cluster is Environment Modules [1], which allow you to define your user environment and the toolset to build and execute your application. They provide a simple way to control dynamically the huge number of combinations that result from various versions of tools and libraries.

The original Environment Modules [2], Tcl/C, has been around since the early 1990s. High-performance computing (HPC) sites have been using them to allow users to specify the combination of tools and libraries they want to use.

One implementation of Environment Modules, Lmod [3], is under constant development and has some unique features that can be very useful even on your desktop if you write code and want to use a variety of tools and libraries. I use Lmod on my desktop and laptop to try new compilers or new compiler versions, as well as new library versions.

Environment Modules Fundamentals

Programmers use a number of compilers, libraries (MPI, compute, and others), and various tools to write applications. For example, someone might code with OpenACC [4] to target GPUs and Fortran for PGI compilers, along with Open MPI, whereas another person might use GNU Compiler Collection (GCC) 8.1 with MPICH. One user might use the Portable, Extensible Toolkit for Scientific Computation (PETSc) [5] to solve their problem, and another user might use OpenBLAS [6].

Environment Modules tools allow users and developers to specify the exact set of tools they want or need and is key to operating an effective HPC system. "Effective" can mean better performance

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