Modifying Design Variables, Constraints, and Objectives

Modifying Design Variables, Constraints, and Objectives#

OpenMDAO provides 3 methods to let the user modify options for design variables, constraints, and objectives after they were set in their respective methods add_design_var, add_constraint, and add_objective. The methods are:

System.set_design_var_options(name, lower=UNDEFINED, upper=UNDEFINED, scaler=UNDEFINED, adder=UNDEFINED, ref=UNDEFINED, ref0=UNDEFINED)[source]

Set options for design vars in the model.

Can be used to set the options outside of setting them when calling add_design_var

Parameters:

namestr
Name of the variable in this system’s namespace.

lowerfloat or ndarray, optional
Lower boundary for the input.

upperupper or ndarray, optional
Upper boundary for the input.

scalerfloat or ndarray, optional
Value to multiply the model value to get the scaled value for the driver. scaler is second in precedence. adder and scaler are an alterantive to using ref and ref0.

adderfloat or ndarray, optional
Value to add to the model value to get the scaled value for the driver. adder is first in precedence. adder and scaler are an alterantive to using ref and ref0.

reffloat or ndarray, optional
Value of design var that scales to 1.0 in the driver.

ref0float or ndarray, optional
Value of design var that scales to 0.0 in the driver.

System.set_constraint_options(name, ref=UNDEFINED, ref0=UNDEFINED, equals=UNDEFINED, lower=UNDEFINED, upper=UNDEFINED, adder=UNDEFINED, scaler=UNDEFINED, alias=UNDEFINED)[source]

Set options for objectives in the model.

Can be used to set options that were set using add_constraint.

Parameters:

namestr
Name of the response variable in the system.

reffloat or ndarray, optional
Value of response variable that scales to 1.0 in the driver.

ref0float or ndarray, optional
Value of response variable that scales to 0.0 in the driver.

equalsfloat or ndarray, optional
Equality constraint value for the variable.

lowerfloat or ndarray, optional
Lower boundary for the variable.

upperfloat or ndarray, optional
Upper boundary for the variable.

adderfloat or ndarray, optional
Value to add to the model value to get the scaled value for the driver. adder is first in precedence. adder and scaler are an alterantive to using ref and ref0.

scalerfloat or ndarray, optional
Value to multiply the model value to get the scaled value for the driver. scaler is second in precedence. adder and scaler are an alterantive to using ref and ref0.

aliasstr, optional
Alias for this response. Necessary when adding multiple constraints on different indices or slices of a single variable.

System.set_objective_options(name, ref=UNDEFINED, ref0=UNDEFINED, adder=UNDEFINED, scaler=UNDEFINED, alias=UNDEFINED)[source]

Set options for objectives in the model.

Can be used to set options after they have been set by add_objective.

Parameters:

namestr
Name of the response variable in the system.

reffloat or ndarray, optional
Value of response variable that scales to 1.0 in the driver.

ref0float or ndarray, optional
Value of response variable that scales to 0.0 in the driver.

adderfloat or ndarray, optional
Value to add to the model value to get the scaled value for the driver. adder is first in precedence. adder and scaler are an alterantive to using ref and ref0.

scalerfloat or ndarray, optional
Value to multiply the model value to get the scaled value for the driver. scaler is second in precedence. adder and scaler are an alterantive to using ref and ref0.

aliasstr
Alias for this response. Necessary when adding multiple objectives on different indices or slices of a single variable.

Example of Modifying Design Variable, Constraint, and Objective Options#

Here is a simple examples of how these methods can be used for an optimizer example. Let’s say a user runs an optimization, and then based on the result, they want to change the bounds of the constraint, and then re-optimize.

# The initial optimization run

import numpy as np
import openmdao.api as om
from openmdao.test_suite.components.sellar import SellarDerivatives

prob = om.Problem(model=SellarDerivatives())
model = prob.model
model.nonlinear_solver = om.NonlinearBlockGS()

prob.driver = om.ScipyOptimizeDriver()
prob.driver.options['optimizer'] = 'SLSQP'
prob.driver.options['tol'] = 1e-9

model.add_design_var('z', lower=np.array([-10.0, 0.0]), upper=np.array([10.0, 10.0]))
model.add_design_var('x', lower=0.0, upper=10.0)
model.add_objective('obj')
model.add_constraint('con1', upper=0.0)
model.add_constraint('con2', upper=0.0)

prob.setup()
prob.set_solver_print(level=0)
prob.run_driver()
print(f"con1 = {prob.get_val('con1')}")

# modify the constraint and run again

model.set_constraint_options(name='con1', upper=-1.0)
prob.setup()
prob.run_driver()
print(f"con1 = {prob.get_val('con1')}")

Optimization terminated successfully    (Exit mode 0)
            Current function value: 4.173853524784769
            Iterations: 12
            Function evaluations: 12
            Gradient evaluations: 12
Optimization Complete
-----------------------------------
con1 = [-1.]

Modifying Design Variables, Constraints, and Objectives

Contents

Modifying Design Variables, Constraints, and Objectives#

Example of Modifying Design Variable, Constraint, and Objective Options#