Using OpenMDAO v1.7.3 Alpha
I have a simple example OpenMDAO Problem consisting of 2 Implicit Components:
- The first Component uses temperature to calculate voltage
- and the second Component uses voltage to calculate temperature
(code at bottom of question)
Unfortunately, it's failing to converge when I run it in OpenMDAO. I think the problem is that I am not setting initial parameter values. as OpenMDAO is printing the following message to output:
The following params are connected to unknowns that are updated out of order, so their initial values may contain uninitialized unknown values: ['battery_temp_comp.volt']
I have been scouring the documentation but cannot figure out how to set this type of Problem (with Implicit Components) up properly. Any help is appreciated. Thank you!
Code:
from __future__ import print_function
import math as m
import numpy
from openmdao.api import Component, Group, Problem, Newton, ScipyGMRES
class BatteryVoltImplicitComp(Component):
""" A Simple Implicit Component modelling a Battery's Voltage"""
def __init__(self):
super(BatteryVoltImplicitComp, self).__init__()
# Params
self.add_param('temp', 30.0)
# Unknowns
self.add_output('volt', 12.0)
# States
self.add_state('delta', 0.0)
def calc_voltage(self, params, unknowns, resids):
temp = params['temp']
voltage_shift = (25.667 - temp) * 0.02933
return 12.77 + voltage_shift
def solve_nonlinear(self, params, unknowns, resids):
pass
def apply_nonlinear(self, params, unknowns, resids):
print("Params: BatteryVoltImplicitComp.temp: {}".format(params['temp']))
print("Unknowns: BatteryVoltImplicitComp.volt: {}".format(unknowns['volt']))
print("Resids: BatteryVoltImplicitComp.delta: {}".format(resids['delta']))
calculated_voltage = self.calc_voltage(params, unknowns, resids)
resids['delta'] = calculated_voltage - unknowns['volt']
class BatteryTempImplicitComp(Component):
""" A Simple Implicit Component modelling a Battery's Temperature"""
def __init__(self):
super(BatteryTempImplicitComp, self).__init__()
# Params
self.add_param('volt', 12.0)
# Unknowns
self.add_output('temp', 30.0)
# States
self.add_state('delta', 0.0)
def calc_temp(self, params, unknowns, resids):
v = params['volt']
room_temp = 23.0 # celsius
batt_resist = 50e-3
power = v**2 / batt_resist
temp_increase = power / 50 # magic number
return room_temp + temp_increase
def solve_nonlinear(self, params, unknowns, resids):
pass
def apply_nonlinear(self, params, unknowns, resids):
print("Params: BatteryTempImplicitComp.volt: {}".format(params['volt']))
print("Unknowns: BatteryTempImplicitComp.temp: {}".format(unknowns['temp']))
print("Resids: BatteryTempImplicitComp.delta: {}".format(resids['delta']))
calculated_temp = self.calc_temp(params, unknowns, resids)
resids['delta'] = calculated_temp - unknowns['temp']
if __name__ == '__main__':
top = Problem()
root = top.root = Group()
root.add('battery_temp_comp', BatteryTempImplicitComp())
root.add('battery_volt_comp', BatteryVoltImplicitComp())
root.connect('battery_volt_comp.volt', 'battery_temp_comp.volt')
root.connect('battery_temp_comp.temp', 'battery_volt_comp.temp')
root.battery_temp_comp.deriv_options['type'] = 'fd'
root.battery_temp_comp.deriv_options['form'] = 'central'
root.battery_temp_comp.deriv_options['step_size'] = 1.0e-1
root.battery_volt_comp.deriv_options['type'] = 'fd'
root.battery_volt_comp.deriv_options['form'] = 'central'
root.battery_volt_comp.deriv_options['step_size'] = 1.0e-1
root.nl_solver = Newton()
root.ln_solver = ScipyGMRES()
top.setup()
top.run()
print('Solution (battery_volt_comp): volt = {}, temp = {}, resid = {}'.format(top['battery_volt_comp.volt'], top['battery_volt_comp.temp'], top['battery_volt_comp.delta']))
print('Solution (battery_temp_comp): volt = {}, temp = {}, resid = {}'.format(top['battery_temp_comp.volt'], top['battery_temp_comp.temp'], top['battery_temp_comp.delta']))
Output:
########################################Setup: Checking root problem for potential issues...
No recorders have been specified, so no data will be saved. Group '' has the following cycles: [['battery_temp_comp', 'battery_volt_comp']]
The following params are connected to unknowns that are updated out of order, so their initial values may contain uninitialized unknown values: ['battery_temp_comp.volt']
Setup: Check of root problem complete.
########################################Params: BatteryTempImplicitComp.volt: 12.0
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 0.0
Params: BatteryVoltImplicitComp.temp: 30.0
Unknowns: BatteryVoltImplicitComp.volt: 12.0
Resids: BatteryVoltImplicitComp.delta: 0.0
Params: BatteryTempImplicitComp.volt: 12.1
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryTempImplicitComp.volt: 11.9
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryTempImplicitComp.volt: 12.0
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryTempImplicitComp.volt: 12.0
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryVoltImplicitComp.temp: 30.1
Unknowns: BatteryVoltImplicitComp.volt: 12.0
Resids: BatteryVoltImplicitComp.delta: 0.64291311
Params: BatteryVoltImplicitComp.temp: 29.9
Unknowns: BatteryVoltImplicitComp.volt: 12.0
Resids: BatteryVoltImplicitComp.delta: 0.64291311
...
Params: BatteryVoltImplicitComp.temp: nan
Unknowns: BatteryVoltImplicitComp.volt: nan
Resids: BatteryVoltImplicitComp.delta: 0.64291311
[root] NL: NEWTON 1 | FAILED to converge after 1 iterations
Solution (battery_volt_comp): volt = nan, temp = nan, resid = -inf
Solution (battery_temp_comp): volt = nan, temp = nan, resid = -inf
