sourceryinstitute / rocket-science

A case study in modernizing legacy Fortran software

Rocket Science

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This repository contains

• A modern mini-application for simulating solid rocket motors using an object-oriented, functional programming style in Fortran 2018.
• A legacy motor simulator demonstrating the solution of the same governing equations using a procedural programming style in Fortran 77/90.
• A refurbished motor simulator demonstrating one modernization path for making the legacy solver object-oriented but without the radical redesign that affords the above purely functional programming style.

The simulator includes a capability for launching gnuplot to compare results of the three solvers.

Prerequisites

We developed this code using the following package versions

• fpm 0.9.0 package manager and build system,
• gfortran 11.2.0 compiler,
• gnuplot 5.4, patchlevel 2 plotting package, and
• Vegetables 7.2.1 unit testing framework.

Other versions might work also.

Using Rocket-Science

To download, build, and run the simplest version of the mini-app (which uses explicit euler time advancement), and to plot the results with gnuplot installed on macOS, Linux, or Windows Subsystem for Linux, execute the following at a bash or zsh command prompt:

git clone https://github.com/sourceryinstitute/rocket-science
cd rocket-science
fpm run explicit-euler -- "--graph"

which should produce plots much like the thrust history graph below.
Press any button to bring up the next plot. If the run completed successfully, the modern, legacy and refurbished curves will be indistinguishable.

To run a mini-app versions that use 2nd-order Runge Kutta and Runge-Kutta-Fehlberg time advancement, respectively, and to graph the results, execute

fpm run runge-kutta-2nd-order -- "--graph"
fpm run runge-kutta-fehlberg -- "--graph"

Test Fire

To run the rocket-science test suite, execute

fpm test

At the time of this writing, the test suite contains two integration tests: one each comparing the modern and refurbished simulation results to those of the legacy code.