This file provides a brief documentation and information related to the fourth (last) Homework of the course "Scientific Programming for Engineers", fall 2019.
This homework is done by O. Ashtari and A. Sieber.
Last update: 15.01.2020
The optimization routine error_minimization.py is intended to minimize the error on Mercury trajectory (or any other planet of the solar system) by scaling the initial velocity of the planet of interest. The minimization is performed by computing the error between the computed planet trajectory and a reference planet trajectory. This routine calls main.py, therefore, in order to run it, the user must first make sure she/he can launch the particles code through the python interface. Once the requirement is satisfied the error_minimization.py routine can be called as follow:
$ python3 directory_comp directory_ref planet input_file scale nb_steps freq
- directory_comp, the path to the directory containing the computed trajectory data.
- directory_ref, the path to the directory containing the reference trajectory data.
- planet, the planet of interest.
- input_file, the file containing the initial state of the different planets.
- scale, the initial scaling factor (initial guess of the minimization).
- nb_steps, the number of time steps of the simulation within the particles code.
- freq, the dumping frequency at which the particles code writes outputs.
As an example a minimization on Mercury trajectory over 365 days with a dumping frequency of 1 day could be run as such:
$ python3 dumps trajectories mercury init.csv 1.0 365 1
The error_minimization.py routine then prints the scaling factorminimizing the error, the value of this error and the amount of minimization iterations needed to reach an optimum. It moreover plots the evolution of the error versus the scaling factor as shown below:
To comment on this function overload, let's first discuss what is the role of createComputes in the whole code. In the ParticlesFactoryInterface class, createComputes is defined as a function which is to be defined later, if needed. In the constructor of MaterialPointsFactory, createComputes is defined to be the default function (i.e. to be createDefaultComputes.) In the default function, ComputeTemperature is added to the system evolution object. Similarly in the PlanetsFactory where createComputes is defined to be createDefaultComputes in which verlet is added to the system evolution object.