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Interaction graph

The code can generate interaction graphs, which can help debugging, if results are not as expected. This can be enabled with the Debug variable set to interaction_graph.

The following input file

input file


CalculationMode = td
ExperimentalFeatures = yes
FromScratch = yes

Dimensions = 3

%Systems
 "Sun"   | classical_particle
 "Earth" | classical_particle
 "Moon"  | classical_particle
%

%Interactions
 gravity | all_partners
%

#Initial conditions are taken from https://ssd.jpl.nasa.gov/horizons.cgi#top.
# initial condition at time:
# 2458938.500000000 = A.D. 2020-Mar-30 00:00:00.0000 TDB

Earth.ParticleMass = 5.97237e24
%Earth.ParticleInitialPosition
 -147364661998.16476 | -24608859261.610123 | 1665165.2801353487
%
%Earth.ParticleInitialVelocity
 4431.136612956525 | -29497.611635546345 | 0.343475566161544
%

Moon.ParticleMass = 7.342e22
%Moon.ParticleInitialPosition
 -147236396732.81906 | -24234200672.857853 | -11062799.286082389
%
%Moon.ParticleInitialVelocity
 3484.6397238565924 | -29221.007409082802 | 82.53526338876684
%

Sun.ParticleMass = 1.98855e30
%Sun.ParticleInitialPosition
 0.0 | 0.0 | 0.0
%
%Sun.ParticleInitialVelocity
 0.0 | 0.0 | 0.0
%

TDSystemPropagator = verlet
TDPropagationTime = 1

Debug = interaction_graph

gives rise to the following graph:

This graph can be created using the graphviz package.

How to install and use graphviz

On Debian-like systems, graphviz can simply be installed with

sudo apt-get install graphviz

Then, the interaction_graph.dot can be converted into a png file by using:

dot -Tpng interaction_graph.dot > interaction_graph.png