Setting the Order of Subsystems in a Group

By default, subsystems are executed in the same order in which they were added to their parent Group. In order to change this order, use the set_order method.

Group.set_order(new_order)

Specify a new execution order for subsystems in this group.

Parameters:

new_orderlist of str

List of system names in desired new execution order.

The list of names provided to set_order must contain every subsystem that has been added to the Group.

Note

Use caution when setting the order of execution of your subsystems, whether by just calling add_subsystem in a specific order, or by later changing the order using set_order. If you choose an order that doesn’t follow the natural data flow order of your subsystems, your model may take longer to converge.

Usage

Change the execution order of components C1 and C3.

import openmdao.api as om


class ReportOrderComp(om.ExplicitComponent):
    """Adds name to list."""

    def __init__(self, order_list):
        super().__init__()
        self._order_list = order_list

    def compute(self, inputs, outputs):
        self._order_list.append(self.pathname)

# this list will record the execution order of our C1, C2, and C3 components
order_list = []

prob = om.Problem()
model = prob.model

model.add_subsystem('C1', ReportOrderComp(order_list))
model.add_subsystem('C2', ReportOrderComp(order_list))
model.add_subsystem('C3', ReportOrderComp(order_list))

prob.setup()
prob.run_model()

print(order_list)

['C1', 'C2', 'C3']

# reset the shared order list
order_list[:] = []

prob.setup()
# now swap C2 and C1 in the order
model.set_order(['C2', 'C1', 'C3'])

# after changing the order, we must call setup again
prob.setup()
prob.run_model()

print(order_list)

['C2', 'C1', 'C3']