Glossary

Polaris

The python package containing framework for listing, setting up and running tasks, as well as code defining the components, tasks and steps.

Compass

The predecessor to polaris that was focused on MPAS components and did not support task parallelism

Component

This term refers to the collection of tasks associated with one or more E3SM components, ocean for MPAS-Ocean and OMEGA, seaice for MPAS-Seaice, and landice for MALI.

Step

A step is the smallest units of work in polaris that you can run on its own. Each task is made up of a sequence of steps. Currently, these steps run in sequence, but there are plans to allow them to run in parallel with one another (task parallelism) in the near future. Steps are commonly used to create meshes and initial conditions (together or separately), run an E3SM component in standalone mode, and to perform visualization or analysis of the results.

Task

A task is the smallest unit of work that polaris will let a user set up on its own. It is a sequence of one or more steps that a user can either run all together or one at a time. A task in polaris should always be independent of other tasks. Some common examples of tasks are bit-for-bit restart tests, decomposition tests across different numbers of cores, and thread tests with different thread counts. Whereas compass allowed tasks to depend on other tasks, this is discouraged in polaris. Instead, shared steps should be used to support common functionality.

Suite

A collection of tasks that are from the same E3SM component that can be run together with a single command (polaris run <suite>, where <suite> is the suite’s name). Sometimes, suites are used to perform regression testing to make sure new MPAS-model features do not add unexpected changes to simulation results. Typically, this involves providing a “baseline” run of the same suite to compare with. Other types of suites are used to run a sequence of tasks that depend on one another (e.g. creating a mesh, setting up an initial condition, running the model, and processing the output, as in ocean-global-ocean).

Work directory

The location where tasks will be set up and run. The “base work directory” is the root for all E3SM components (and therefore tasks and steps), and is the path passed with the -w or -b flags to polaris setup and polaris suite. The work directory for a task or step its location within base work directory (the base work directory plus its relative path)

Package

A python package is a directory that has a file called __init__.py. That file can be empty or it can have code in it. If there is code in __init__.py, it gets imported as if it were directly in the package (you never include __init__ in an import statement).

Module

Python modules are python files that can be imported by other python files (so they’re not just scripts). Nearly every single file ending in .py in the polaris package is a module. The __init__.py files are a special case, that may define a module with the name of the package (directory) that __init__.py is in.