def arbitrary_partition(disjunction, P):
"""
Returns a valid partition into P sets of the variables that appear in
algebraic additively separable constraints in the Disjuncts in
'disjunction'. Note that this method may return an invalid partition
if the constraints are not additively separable!
Arguments:
----------
disjunction : A Disjunction object for which the variable partition will be
created.
P : An int, the number of partitions
"""
# collect variables
v_set = ComponentSet()
for disj in disjunction.disjuncts:
v_set.update(
get_vars_from_components(disj,
Constraint,
descend_into=Block,
active=True))
# assign them to partitions
partitions = [ComponentSet() for i in range(P)]
for i, v in enumerate(v_set):
partitions[i % P].add(v)
return partitions
def _apply_to(self, instance, **kwds):
if not instance.ctype in (Block, Disjunct):
raise GDP_Error(
"Transformation called on %s of type %s. 'instance'"
" must be a ConcreteModel, Block, or Disjunct (in "
"the case of nested disjunctions)." %
(instance.name, instance.ctype))
try:
self._config = self.CONFIG(kwds.pop('options', {}))
self._config.set_value(kwds)
self._transformation_blocks = {}
if not self._config.assume_fixed_vars_permanent:
fixed_vars = ComponentMap()
for v in get_vars_from_components(instance,
Constraint,
include_fixed=True,
active=True,
descend_into=(Block,
Disjunct)):
if v.fixed:
fixed_vars[v] = value(v)
v.fixed = False
self._apply_to_impl(instance)
finally:
# restore fixed variables
if not self._config.assume_fixed_vars_permanent:
for v, val in fixed_vars.items():
v.fix(val)
del self._config
del self._transformation_blocks
def get_vars_from_component(block, ctype):
"""Determine all variables used in active components within a block.
Parameters
----------
block: Block
The block to search for components. This is a recursive
generator and will descend into any active sub-Blocks as well.
ctype: class
The component type (typically either :py:class:`Constraint` or
:py:class:`Objective` to search for).
"""
return get_vars_from_components(block, ctype, active=True,
descend_into=True)