Skip to content

Latest commit

 

History

History
100 lines (69 loc) · 2.55 KB

POEM_092.md

File metadata and controls

100 lines (69 loc) · 2.55 KB
Raw

POEM ID: 092
Title: User-defined function hook for pre-processing option set.
authors: Kenneth-T-Moore (Ken Moore)
Competing POEMs:
Related POEMs:
Associated implementation PR: PR 3040

Status:

  • Active
  • Requesting decision
  • Accepted
  • Rejected
  • Integrated

Motivation

OpenMDAO's component options feature is sometimes used to define constant quantities with units. When coupled with the top-level setting of system options, this creates as situation where an option might be specified in the wrong units. As a general solution, this POEM proposes the addition of a pre-set function hook that the user can define to pre-process a value and compute a new value before setting the option in a component. This hook could be used to convert units, or it could be used for other processing.

Proposed Solution

The only API change from this POEM is an additional argument to the declare method of OptionDictionary. The new argument is "set_function", which takes a function whose input parameters are a dictionary that contains the option's metadata and a value, and whose return is a new value.

Example

import openmdao.api as om
from openmdao.utils.units import convert_units


def units_setter(opt_meta, value):
    """
    Check and convert new units tuple into

    Parameters
    ----------
    opt_meta : dict
        Dictionary of entries for the option.
    value : any
        New value for the option.

    Returns
    -------
    any
        Post processed value to set into the option.
    """
    new_val, new_units = value
    old_val, units = opt_meta['val']

    converted_val = convert_units(new_val, new_units, units)
    return (converted_val, units)


class AviaryComp(om.ExplicitComponent):

    def setup(self):

        self.add_input('x', 3.0)
        self.add_output('y', 3.0)

    def initialize(self):
        self.options.declare('length', default=(12.0, 'inch'),
                             set_function=units_setter)

    def compute(self, inputs, outputs):
        length = self.options['length'][0]

        x = inputs['x']
        outputs['y'] = length * x


class Fakeviary(om.Group):

    def setup(self):
        self.add_subsystem('mass', AviaryComp())


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

model.add_subsystem('statics', Fakeviary())

prob.model_options['*'] = {'length': (2.0, 'ft')}
prob.setup()

prob.run_model()
print('The following should be 72 if the units convert correctly.')
print(prob.get_val('statics.mass.y'))
print('done')

Notes