# 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)