Adding a problem

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Adding a problem#

Problem setups are defined in a problems/ subdirectory under each solver. For example, the problem setups for compressible are here: python-hydro/pyro2

When you install pyro via pip, these problem setups become available. At the moment, the way to add a new problem is to directly put files into these directories.

Tip

If you are working on adding problems, it is recommended that you install pyro from source and do it as an editable install as:

pip install -e .

Every problem needs a python module of the form problem_name.py. This will define the runtime parameters that the problem expects and do the initialization of the state variables.

Many problems will also provide an inputs file that overrides some of the runtime parameter defaults (like the domain size and BCs) to be appropriate for this problem.

“problem.py”#

A python module named after the problem (we’ll call it problem.py here) provides the following:

  • PROBLEM_PARAMS : this is a dictionary (it can be empty, {}) that defines the runtime parameters that are needed to this problem setup. For instance, for the compressible sod problem:

    PROBLEM_PARAMS = {"sod.direction": "x",
                  "sod.dens_left": 1.0,
                  "sod.dens_right": 0.125,
                  "sod.u_left": 0.0,
                  "sod.u_right": 0.0,
                  "sod.p_left": 1.0,
                  "sod.p_right": 0.1}

    Each key in the dictionary should be of the form problem-name.parameter, and the values are the default value of the parameter.

    Any of these runtime parameters can be overridden in an inputs file or on the commandline (when running via pyro_sim.py) or via the inputs_dict keyword argument (when running via the Pyro class).

  • DEFAULT_INPUTS : this is the name of an inputs file to be read in by default when using the Pyro class interface. It can be None.

    This is not used when running via pyro_sim.py.

  • init_data() : this is the main initialization routine. It has the signature:

    def init_data(my_data, rp)

    where

    • my_data is a CellCenterData2d or FV2d object. The Grid object can be obtained from this as needed.

    • rp is a RuntimeParameters object. Any of the runtime parameters (including the problem-specific ones defined via PROBLEM_PARAMS) can be accessed via this.

    Note

    The interface for init_data is the same for all solvers.

    The job of init_data is to initialize the state data that is managed by the my_data object passed in. Exactly which variables are included there will depend on the solver.

  • finalize() : this is called at the very end of evolution. It is meant to output instructions to the user on how the can analyze the data. It takes no arguments.

Important

Once the problem is defined, you need to add the problem name to the __all__ list in the __init__.py file in the problems/ sub-directory. This lets python know about the problem.

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