Source code for pyomo.contrib.preprocessing.plugins.init_vars

"""Automatically initialize variables."""
from __future__ import division

import textwrap

from pyomo.core.base.var import Var
from pyomo.core.base.plugin import TransformationFactory
from pyomo.core.expr.numvalue import value
from pyomo.core.plugins.transform.hierarchy import IsomorphicTransformation


[docs]@TransformationFactory.register( 'contrib.init_vars_midpoint', doc="Initialize non-fixed variables to the midpoint of their bounds.") class InitMidpoint(IsomorphicTransformation): """Initialize non-fixed variables to the midpoint of their bounds. - If the variable does not have bounds, set the value to zero. - If the variable is missing one bound, set the value to that of the existing bound. """ def _apply_to(self, instance, overwrite=False): """Apply the transformation. Kwargs: overwrite: if False, transformation will not overwrite existing variable values. """ for var in instance.component_data_objects( ctype=Var, descend_into=True): if var.fixed: continue if var.value is not None and not overwrite: continue if var.lb is None and var.ub is None: # If LB and UB do not exist, set variable value to 0 var.set_value(0) elif var.lb is None: # if one bound does not exist, set variable value to the other var.set_value(value(var.ub)) elif var.ub is None: # if one bound does not exist, set variable value to the other var.set_value(value(var.lb)) else: var.set_value((value(var.lb) + value(var.ub)) / 2.)
[docs]@TransformationFactory.register( 'contrib.init_vars_zero', doc="Initialize non-fixed variables to zero.") class InitZero(IsomorphicTransformation): """Initialize non-fixed variables to zero. - If setting the variable value to zero will violate a bound, set the variable value to the relevant bound value. """ def _apply_to(self, instance, overwrite=False): """Apply the transformation. Kwargs: overwrite: if False, transformation will not overwrite existing variable values. """ for var in instance.component_data_objects( ctype=Var, descend_into=True): if var.fixed: continue if var.value is not None and not overwrite: continue if var.lb is not None and value(var.lb) > 0: var.set_value(value(var.lb)) elif var.ub is not None and value(var.ub) < 0: var.set_value(value(var.ub)) else: var.set_value(0)