def test_is_constant(self):
p = parameter()
self.assertEqual(p.is_constant(), False)
self.assertEqual(is_constant(p), False)
p.value = 1.0
self.assertEqual(p.is_constant(), False)
self.assertEqual(is_constant(p), False)
def test_is_constant(self):
v = variable()
self.assertEqual(v.is_constant(), False)
self.assertEqual(is_constant(v), False)
self.assertEqual(v.fixed, False)
self.assertEqual(v.value, None)
v.value = 1.0
self.assertEqual(v.is_constant(), False)
self.assertEqual(is_constant(v), False)
self.assertEqual(v.fixed, False)
self.assertEqual(v.value, 1.0)
v.fix()
self.assertEqual(v.is_constant(), False)
self.assertEqual(is_constant(v), False)
self.assertEqual(v.fixed, True)
self.assertEqual(v.value, 1.0)
v.value = None
self.assertEqual(v.is_constant(), False)
self.assertEqual(is_constant(v), False)
self.assertEqual(v.fixed, True)
self.assertEqual(v.value, None)
v.free()
self.assertEqual(v.is_constant(), False)
self.assertEqual(is_constant(v), False)
self.assertEqual(v.fixed, False)
self.assertEqual(v.value, None)
def test_is_constant(self):
e = self._ctype_factory()
self.assertEqual(e.is_constant(), False)
self.assertEqual(is_constant(e), False)
e.expr = 1
self.assertEqual(e.is_constant(), False)
self.assertEqual(is_constant(e), False)
p = parameter()
self.assertEqual(p.is_constant(), False)
self.assertEqual(is_constant(p), False)
p.value = 2
e.expr = p + 1
self.assertEqual(e.is_constant(), False)
self.assertEqual(is_constant(e), False)
def test_is_constant(self):
v = variable()
e = noclone(v)
self.assertEqual(e.is_constant(), False)
self.assertEqual(is_constant(e), False)
v.fix(1)
self.assertEqual(e.is_constant(), False)
self.assertEqual(is_constant(e), False)
p = parameter()
e = noclone(p)
self.assertEqual(p.is_constant(), False)
self.assertEqual(is_constant(p), False)
self.assertEqual(is_constant(noclone(1)), True)
def expr(self, expr):
self._equality = False
if expr is None:
self.body = None
self.lb = None
self.ub = None
return
_expr_type = expr.__class__
if _expr_type is tuple: # or expr_type is list:
#
# Form equality expression
#
if len(expr) == 2:
arg0 = expr[0]
if arg0 is not None:
arg0 = as_numeric(arg0)
arg1 = expr[1]
if arg1 is not None:
arg1 = as_numeric(arg1)
# assigning to the rhs property
# will set the equality flag to True
if arg1 is None or (not arg1._potentially_variable()):
self.rhs = arg1
self.body = arg0
elif arg0 is None or (not arg0._potentially_variable()):
self.rhs = arg0
self.body = arg1
else:
with EXPR.bypass_clone_check():
self.rhs = ZeroConstant
self.body = arg0
self.body -= arg1
#
# Form inequality expression
#
elif len(expr) == 3:
arg0 = expr[0]
if arg0 is not None:
arg0 = as_numeric(arg0)
if arg0._potentially_variable():
raise ValueError(
"Constraint '%s' found a 3-tuple (lower,"
" expression, upper) but the lower "
"value was not data or an expression "
"restricted to storage of data."
% (self.name))
arg1 = expr[1]
if arg1 is not None:
arg1 = as_numeric(arg1)
arg2 = expr[2]
if arg2 is not None:
arg2 = as_numeric(arg2)
if arg2._potentially_variable():
raise ValueError(
"Constraint '%s' found a 3-tuple (lower,"
" expression, upper) but the upper "
"value was not data or an expression "
"restricted to storage of data."
% (self.name))
self.lb = arg0
self.body = arg1
self.ub = arg2
else:
raise ValueError(
"Constraint '%s' assigned a tuple "
"of length %d. Expecting a tuple of "
"length 2 or 3:\n"
"Equality: (body, rhs)\n"
"Inequality: (lb, body, ub)"
% (self.name, len(expr)))
relational_expr = False
else:
try:
relational_expr = expr.is_relational()
if not relational_expr:
raise ValueError(
"Constraint '%s' does not have a proper "
"value. Found '%s'\nExpecting a tuple or "
"equation. Examples:"
"\n summation(model.costs) == model.income"
"\n (0, model.price[item], 50)"
% (self.name, str(expr)))
except AttributeError:
msg = ("Constraint '%s' does not have a proper "
"value. Found '%s'\nExpecting a tuple or "
"equation. Examples:"
"\n summation(model.costs) == model.income"
"\n (0, model.price[item], 50)"
% (self.name, str(expr)))
if type(expr) is bool:
msg += ("\nNote: constant Boolean expressions "
"are not valid constraint expressions. "
"Some apparently non-constant compound "
"inequalities (e.g. 'expr >= 0 <= 1') "
"can return boolean values; the proper "
"form for compound inequalities is "
"always 'lb <= expr <= ub'.")
raise ValueError(msg)
#
# Special check for chainedInequality errors like "if var <
# 1:" within rules. Catching them here allows us to provide
# the user with better (and more immediate) debugging
# information. We don't want to check earlier because we
# want to provide a specific debugging message if the
# construction rule returned True/False; for example, if the
# user did ( var < 1 > 0 ) (which also results in a non-None
# chainedInequality value)
#
if EXPR.generate_relational_expression.chainedInequality is not None:
raise TypeError(EXPR.chainedInequalityErrorMessage())
#
# Process relational expressions
# (i.e. explicit '==', '<', and '<=')
#
if relational_expr:
if _expr_type is EXPR._EqualityExpression:
# Equality expression: only 2 arguments!
_args = expr._args
# Explicitly dereference the original arglist (otherwise
# this runs afoul of the getrefcount logic)
expr._args = []
# assigning to the rhs property
# will set the equality flag to True
if not _args[1]._potentially_variable():
self.rhs = _args[1]
self.body = _args[0]
elif not _args[0]._potentially_variable():
self.rhs = _args[0]
self.body = _args[1]
else:
with EXPR.bypass_clone_check():
self.rhs = ZeroConstant
self.body = _args[0]
self.body -= _args[1]
else:
# Inequality expression: 2 or 3 arguments
if expr._strict:
try:
_strict = any(expr._strict)
except:
_strict = True
if _strict:
#
# We can relax this when:
# (a) we have a need for this
# (b) we have problem writer that
# explicitly handles this
# (c) we make sure that all problem writers
# that don't handle this make it known
# to the user through an error or
# warning
#
raise ValueError(
"Constraint '%s' encountered a strict "
"inequality expression ('>' or '<'). All"
" constraints must be formulated using "
"using '<=', '>=', or '=='."
% (self.name))
_args = expr._args
# Explicitly dereference the original arglist (otherwise
# this runs afoul of the getrefcount logic)
expr._args = []
if len(_args) == 3:
if _args[0]._potentially_variable():
raise ValueError(
"Constraint '%s' found a double-sided "
"inequality expression (lower <= "
"expression <= upper) but the lower "
"bound was not data or an expression "
"restricted to storage of data."
% (self.name))
if _args[2]._potentially_variable():
raise ValueError(
"Constraint '%s' found a double-sided "\
"inequality expression (lower <= "
"expression <= upper) but the upper "
"bound was not data or an expression "
"restricted to storage of data."
% (self.name))
self.lb = _args[0]
self.body = _args[1]
self.ub = _args[2]
else:
if not _args[1]._potentially_variable():
self.lb = None
self.body = _args[0]
self.ub = _args[1]
elif not _args[0]._potentially_variable():
self.lb = _args[0]
self.body = _args[1]
self.ub = None
else:
with EXPR.bypass_clone_check():
self.lb = None
self.body = _args[0]
self.body -= _args[1]
self.ub = ZeroConstant
#
# Replace numeric bound values with a NumericConstant object,
# and reset the values to 'None' if they are 'infinite'
#
if (self.lb is not None) and is_constant(self.lb):
val = self.lb()
if not pyutilib.math.is_finite(val):
if val > 0:
raise ValueError(
"Constraint '%s' created with a +Inf lower "
"bound." % (self.name))
self.lb = None
if (self.ub is not None) and is_constant(self.ub):
val = self.ub()
if not pyutilib.math.is_finite(val):
if val < 0:
raise ValueError(
"Constraint '%s' created with a -Inf upper "
"bound." % (self.name))
self.ub = None
#
# Error check, to ensure that we don't have an equality
# constraint with 'infinite' RHS
#
assert not (self.equality and (self.lb is None))
assert (not self.equality) or (self.lb is self.ub)
def is_constant(self):
"""A boolean indicating whether this expression is constant."""
return is_constant(self._expr)
