Setting up your own problem

The best way to set up a new problem is to find an existing problem setup that is similar. The main steps are:

• Write a Riemann solver (if solving a new system of equations)
• Set up the Makefile
• Write the initialization script
• Write routines for source terms, custom boundary conditions, or other customizations
• Write a setplot.py file for visualization

Writing a Riemann solver

The Riemann package has solvers for many hyperbolic systems. If your problem involves a new system, you will need to write your own Riemann solver. Please then contribute your solver to the package by sending a pull request on Github or e-mailing one of the developers.

For very simple problems in one dimension, it may be worthwhile to write the Riemann solver in Python, especially if you are more comfortable with Python than with Fortran. For two-dimensional problems, or one-dimensional problems requiring fine grids (or if you are impatient) the solver should be written in Fortran. The best approach is generally to find a similar solver in the Riemann package and modify it to solve your system.

Setting up the Makefile

Generally you can just copy the Makefile from an example in pyclaw/apps and replace the value of RP_SOURCES. Make sure the example you choose has the same dimensionality. Also be sure to use the f-wave targets if your Riemann solver is an f-wave solver.

Writing the initialization script

This script should:

• Import the appropriate package (pyclaw or petclaw)
• Instantiate a :class:`~pyclaw.solver.Solver`
• Set the Riemann solver if using a Python Riemann solver
• Set solver.mwaves
• Set the boundary conditions
• Instantiate some :class:`~pyclaw.grid.Dimension` object(s) and a :class:`~pyclaw.grid.Grid`
• Set any required global values in aux_global
• Set grid.meqn and grid.mbc
• Set the initial condition (grid.q)

Usually the script then instantiates a :class:`~pyclaw.controller.Controller`, sets the initial solution and solver, and calls :meth:`~pyclaw.controller.Controller.run`.