Propagate State from scaling tools throws an error if any variable is uninitialized #2817
Description
Summary
propagate_state from Pyomo's scaling tools cannot handle if any variables in the model are uninitialized.
In the original IDAES model this was encountered in (the ControlVolume1D), we have unpaired material and energy difference terms along either the x=0 or x=1 boundary (depending on the discretization direction). Presently, we use the fact those terms are uninitialized in initialization methods to determine whether the user has provided an initial guess or not, so just initializing them at zero isn't an immediate solution.
Steps to reproduce the issue
Minimum example:
import pyomo.environ as pyo
m = pyo.ConcreteModel()
m.x = pyo.Var()
m.y = pyo.Var()
m.z = pyo.Var()
m.x.value = 1
m.y.value = 1
@m.Constraint()
def eqn1(b):
return 10 * b.y == b.x
m.scaling_factor = pyo.Suffix(direction=pyo.Suffix.EXPORT)
m.scaling_factor[m.x] = 0.1
m.scaling_factor[m.eqn1] = 0.1
pyomo_scaling = pyo.TransformationFactory('core.scale_model')
m_scaled = pyomo_scaling.create_using(m, rename=False)
pyomo_scaling.propagate_solution(m_scaled, m)
Error Message
ERROR: evaluating object as numeric value: z
(object: <class 'pyomo.core.base.var.ScalarVar'>)
No value for uninitialized NumericValue object z
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Cell In[3], line 26
21 m_scaled = pyomo_scaling.create_using(m, rename=False)
23 # solver_obj = pyo.SolverFactory('ipopt')
24 # solver_obj.solve(m_scaled, tee=True)
---> 26 pyomo_scaling.propagate_solution(m_scaled, m)
File ~\.conda\envs\idaes-newer\lib\site-packages\pyomo\core\plugins\transform\scaling.py:360, in ScaleModel.propagate_solution(self, scaled_model, original_model)
356 original_v = original_model.find_component(original_v_path)
358 for k in scaled_v:
359 original_v[k].set_value(
--> 360 value(scaled_v[k]) / component_scaling_factor_map[scaled_v[k]],
361 skip_validation=True,
362 )
363 if check_reduced_costs and scaled_v[k] in scaled_model.rc:
364 original_model.rc[original_v[k]] = scaled_model.rc[scaled_v[k]] * component_scaling_factor_map[
365 scaled_v[k]] / objective_scaling_factor
File ~\.conda\envs\idaes-newer\lib\site-packages\pyomo\core\expr\numvalue.py:140, in value(obj, exception)
138 tmp = obj(exception=True)
139 if tmp is None:
--> 140 raise ValueError(
141 "No value for uninitialized NumericValue object %s"
142 % (obj.name,))
143 return tmp
144 except TemplateExpressionError:
145 # Template expressions work by catching this error type. So
146 # we should defer this error handling and not log an error
147 # message.
ValueError: No value for uninitialized NumericValue object zPyomo version 6.5.1a0