# 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 `qutip.mesolve`

and `qutip.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 `qutip.mesolve`

and `qutip.mcsolve`

function:

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

or:

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