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POEM ID: 061
Title: The openmdao:allow_desvar tag
authors: @robfalck
Competing POEMs:
Related POEMs:
Associated implementation PR: #2350

Status:

  • Active
  • Requesting decision
  • Accepted
  • Rejected
  • Integrated

Motivation

Currently a user can assign any output as a design variable, though this is almost certainly unwanted behavior. Still, the possibility exists that a user may wish to create an IndepVarComp-like component of their own, so we cannot simply disallow design variables on all non IVC outputs.

import openmdao.api as om

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

prob.driver = om.ScipyOptimizeDriver()

root.add_subsystem('initial_comp', om.ExecComp(['x = 10']), promotes_outputs=['x'])

outer_group = root.add_subsystem('outer_group', om.Group(), promotes_inputs=['x'])
inner_group = outer_group.add_subsystem('inner_group', om.Group(), promotes_inputs=['x'])

c1 = inner_group.add_subsystem('c1', om.ExecComp(['y = x * 2.0',  'z = x ** 2']),  promotes_inputs=['x'])

c1.add_design_var('x', lower=0, upper=5)
c1.add_constraint('y', lower=1.5)
c1.add_objective('z')

prob.setup()

prob.run_driver()
prob.list_problem_vars()

Solution

To get around this, we will create a new tag: openmdao:allow_desvar, and any attempt to assign a design variable to an output without this tag will result in an exception be raised.

By default, this tag will be applied to outputs of

  • IndepVarComp
  • ImplicitComponent

Checking whether a variable can be validly made a design variable is then just a matter of testing if it has this tag applied to it.

In the rare corner case that a user implements their own IndepVarComp-like component, they will be able to tag outputs to allow them to be design variables.