Specifying parameters

When calling ODEIntegrator, there are two ways of specifying the static or dynamic parameters.

1. Fixed parameters

If the static or dynamic parameters are fixed, the simplest way to specify them is to pass them in when calling ODEIntegrator:

import numpy as np
import matplotlib.pyplot as plt

from openmdao.api import Problem

from ozone.api import ODEIntegrator
from ozone.tests.ode_function_library.getting_started_oc_func \
    import GettingStartedOCFunction

num = 101

ode_function = GettingStartedOCFunction()
formulation = 'solver-based'
method_name = 'RK4'
times = np.linspace(0., 3., num)
initial_conditions = {'x': 0., 'y': 0., 'v': 0.}

# Here, the dynamic parameter array is passed in
dynamic_parameters = {'theta': np.zeros((num, 1))}

integrator = ODEIntegrator(ode_function, formulation, method_name,
    times=times, initial_conditions=initial_conditions,
    dynamic_parameters=dynamic_parameters)

prob = Problem(model=integrator)
prob.setup(check=False)
prob.run_model()

plt.plot(prob['times'], prob['state:y'][:, 0])
plt.xlabel('t')
plt.ylabel('y')
plt.show()

2. Variable parameters

If the static or dynamic parameters vary during optimization, they must be connected from an external component:

import numpy as np
import matplotlib.pyplot as plt

from openmdao.api import Problem, IndepVarComp

from ozone.api import ODEIntegrator
from ozone.tests.ode_function_library.getting_started_oc_func \
    import GettingStartedOCFunction

num = 101

ode_function = GettingStartedOCFunction()
formulation = 'solver-based'
method_name = 'RK4'
times = np.linspace(0., 3., num)
initial_conditions = {'x': 0., 'y': 0., 'v': 0.}

integrator = ODEIntegrator(ode_function, formulation, method_name,
    times=times, initial_conditions=initial_conditions)

# Below, the parameter is connected from an external component.
prob = Problem()
prob.model.add_subsystem('parameter_comp',
    IndepVarComp('theta', val=0., shape=(num, 1)))
prob.model.add_subsystem('integrator_group', integrator)
prob.model.connect('parameter_comp.theta', 'integrator_group.dynamic_parameter:theta')
prob.setup(check=False)
prob.run_model()

plt.plot(prob['integrator_group.times'], prob['integrator_group.state:y'][:, 0])
plt.xlabel('t')
plt.ylabel('y')
plt.show()