"""
Define the NonlinearRunOnce class.

This is a simple nonlinear solver that just runs the system once.
"""
from openmdao.recorders.recording_iteration_stack import Recording
from openmdao.solvers.solver import NonlinearSolver
from openmdao.utils.mpi import multi_proc_fail_check


class NonlinearRunOnce(NonlinearSolver):
    """
    Simple solver that runs the containing system once.

    This is done without iteration or norm calculation.

    Parameters
    ----------
    **kwargs : dict
        Options dictionary.
    """

    SOLVER = 'NL: RUNONCE'

    def solve(self):
        """
        Run the solver.
        """
        system = self._system()

        with Recording('NLRunOnce', 0, self) as rec:
            # If this is a parallel group, transfer all at once then run each subsystem.
            if len(system._subsystems_myproc) != len(system._subsystems_allprocs):
                system._transfer('nonlinear', 'fwd')

                with multi_proc_fail_check(system.comm):
                    for subsys in system._subsystems_myproc:
                        subsys._solve_nonlinear()

            # If this is not a parallel group, transfer for each subsystem just prior to running it.
            else:
                self._gs_iter()

            rec.abs = 0.0
            rec.rel = 0.0

    def _declare_options(self):
        """
        Declare options before kwargs are processed in the init method.
        """
        # Remove unused options from base options here, so that users
        #  attempting to set them will get KeyErrors.
        self.options.undeclare("atol")
        self.options.undeclare("rtol")

        # this solver does not iterate
        self.options.undeclare("maxiter")
        self.options.undeclare("err_on_non_converge")
