Degenerate Conic

Algorithms • Modern Fortran Programming • Orbital Mechanics

Jan 27, 2018

Directed Acyclic Graph Library

dag_example

I released a new open source project on GitHub: DAGLIB, a modern Fortran library for manipulation of directed acyclic graphs (DAGs). This is based on some code I showed in a previous post. Right now, it's very basic, but you can use it to define DAGs, generate the topologically sorted order, and generate a "dot" file that can be used by GraphViz to visualize the DAG (such as the one shown at right).

In my recent AIAA paper I showed the following DAG representing how we have designed the upcoming Orion EM-1 mission:

dependency

During Exploration Mission-1, Orion will venture thousands of miles beyond the moon during an approximately three week mission.

During Exploration Mission-1, Orion will venture thousands of miles beyond the moon during an approximately three week mission. [NASA]

In this case, the DAG represents the dependencies among different mission attributes (which represent maneuvers, coast phases, constraints, other algorithms, etc). To simulate the entire end-to-end mission, each element must be evaluated in the correct order such that all the dependencies are met. In this same paper, we also discuss other algorithms and their implementation in modern Fortran which may be familiar to readers of this blog.

See also

  1. J. Williams, R. D. Falck, and I. B. Beekman. "Application of Modern Fortran to Spacecraft Trajectory Design and Optimization", 2018 Space Flight Mechanics Meeting, AIAA SciTech Forum, (AIAA 2018-1451)
  2. (Modern?) Fortran directed graphs library [comp.lang.fortran] May 6, 2016
  3. JSON-Fortran GraphViz Example (how to generate a directed graph from a JSON structure), Apr 22, 2017
  4. The Ins and Outs of NASA’s First Launch of SLS and Orion, NASA, Nov. 27, 2015
posted at 09:34  ·   ·  DAG  Fortran  GitHub  NASA  Orion