Setting Options for the Dynamics Solvers

Occasionally it is necessary to change the built in parameters of the dynamics solvers used by for example the mesolve and mcsolve functions. The options for all dynamics solvers may be changed by using the dictionaries.

options = {"store_states": True, "atol": 1e-12}

Supported items come from 2 sources, the solver and the ODE integration method. Supported solver options and their default can be seen using the class interface:

help(MESolver.options)

Options supported by the ODE integration depend on the “method” options of the solver, they can be listed through the integrator method of the solvers:

help(MESolver.integrator("adams").options)

See Integrator for a list of supported methods.

As an example, let us consider changing the integrator, turn the GUI off, and strengthen the absolute tolerance.

options = {"method": "bdf", "atol": 1e-10, "progress_bar": False}

To use these new settings we can use the keyword argument options in either the mesolve and mcsolve function:

>>> mesolve(H0, psi0, tlist, c_op_list, [sigmaz()], options=options)

or:

>>> MCSolver(H0, c_op_list, options=options)

Progress Bars

The progress_bar solver option controls how run progress is displayed. For example:

options = {"progress_bar": "text"}

Common values are:

  • "text": periodic text output to stdout.

  • "enhanced": a single-line text progress bar.

  • "tqdm": uses tqdm (requires the tqdm package).

  • "" (or False / None): disable progress output.

In notebook contexts, "html" is also available and uses an HTML-based progress display.

The progress_kwargs option passes keyword arguments to the selected bar. For QuTiP’s built-in text bars, a common argument is chunk_size:

options = {
    "progress_bar": "text",
    "progress_kwargs": {"chunk_size": 5},
}