def test_breakdown(self, lhs, rhs):
constraint = LpConstraint(lhs, 'eq', rhs, 'test_constraint')
lower_bound_constraint, upper_bound_constraint = constraint.breakdown()
assert lower_bound_constraint.sense == 'geq'
assert lower_bound_constraint.name == 'test_constraint_lb'
assert upper_bound_constraint.sense == 'leq'
assert upper_bound_constraint.name == 'test_constraint_ub'
def test_to_lp_terms(self, x, y):
# 2x + 3y + 7
lhs = LpExpression('lhs', {x: 2, y: 3}, 7)
# x + 5y + 2
rhs = LpExpression('rhs', {x: 1, y: 5}, 2)
constraint = LpConstraint(lhs, 'leq', rhs, 'test_constraint')
assert constraint.to_lp_terms() == ['x', '- 2 y', '<=', '-5']
def test_invalid_sense(self, lhs):
with pytest.raises(ValueError) as e:
LpConstraint(lhs, 'invalid')
assert 'sense' in e.message.lower()
with pytest.raises(ValueError) as e:
LpConstraint(lhs, 1)
assert 'sense' in e.message.lower()
def test_lower_bound(self, lhs, rhs):
constraint = LpConstraint(lhs, 'leq', rhs, 'test_constraint')
assert constraint.lower_bound is None
assert constraint.upper_bound == -5
constraint = LpConstraint(lhs, 'geq', rhs, 'test_constraint')
assert constraint.upper_bound is None
assert constraint.lower_bound == -5
constraint = LpConstraint(lhs, 'eq', rhs, 'test_constraint')
assert constraint.upper_bound == -5
assert constraint.lower_bound == -5
def test_invalid_exprs(self, lhs):
# test LHS
with pytest.raises(ValueError) as e:
LpConstraint('invalid', 'leq')
assert 'lhs' in e.message.lower()
# test RHS
with pytest.raises(ValueError) as e:
LpConstraint(lhs, 'leq', 'invalid')
assert 'rhs' in e.message.lower()
def test_check(self, x, y, lhs, rhs):
lp_constraint = LpConstraint(lhs, 'geq', rhs)
x.set_value(5)
y.set_value(0)
assert lp_constraint.check()
lp_constraint = LpConstraint(lhs, 'leq', rhs)
assert not lp_constraint.check()
lp_constraint.slack = True
lp_constraint.slack_variable.set_value(100)
assert lp_constraint.check()
lp_constraint.slack = False
assert not lp_constraint.check()
def test_add_constraint(self, problem, x):
rhs = LpExpression('rhs', {x: 1})
lhs = LpExpression('lhs', {x: 1}, 2)
constraint = LpConstraint(rhs, 'geq', lhs, 'constraint')
problem.add_constraint(constraint)
assert problem.lp_constraints[constraint.name] == constraint
assert problem.lp_variables[x.name] == x
constraint = LpConstraint(lhs, 'geq', rhs, 'constraint')
with pytest.raises(Exception) as e:
problem.add_constraint(constraint)
assert e.value.args == (
'LP constraint name %s conflicts with an existing LP constraint' %
constraint.name, )
with pytest.raises(Exception) as e:
problem.add_constraint(10)
assert e.value.args == ('%s is not an LpConstraint' % 10, )
def test_write_no_objective(self, problem, x):
rhs = LpExpression('rhs', {x: 1})
lhs = LpExpression('lhs', {}, -2)
constraint = LpConstraint(rhs, 'geq', lhs, 'constraint')
problem.add_constraint(constraint)
buffer = StringIO()
with pytest.raises(Exception) as e:
problem.write_lp(buffer)
assert e.value.args == ('No objective', )
def test_write(self, problem, x):
objective = LpObjective(name='minimize_cpm',
expression={x: 998},
constant=8)
rhs = LpExpression('rhs', {x: 1})
lhs = LpExpression('lhs', {}, -2)
constraint = LpConstraint(rhs, 'geq', lhs, 'constraint')
problem.add_constraint(constraint)
problem.set_objective(objective)
buffer = StringIO()
problem.write_lp(buffer)
flipy_string = buffer.getvalue()
assert flipy_string == '\\* test_problem *\\\nMinimize\nminimize_cpm: 998 x + 8\nSubject To\nconstraint: x >= -2\nBounds\nx <= 10\nEnd'
def test_write_with_empty_constraint(self, problem, x):
objective = LpObjective(name='minimize_cpm',
expression={x: 998},
constant=8,
sense=Maximize)
constraint = LpConstraint(LpExpression('lhs', {x: 0}), 'leq',
LpExpression('rhs', {}), 'constraint')
problem.add_constraint(constraint)
problem.set_objective(objective)
buffer = StringIO()
problem.write_lp(buffer)
flipy_string = buffer.getvalue()
assert flipy_string == '\\* test_problem *\\\nMaximize\nminimize_cpm: 998 x + 8\nSubject To\nBounds\nx <= 10\nEnd'
def test_write_slack(self, problem, x):
objective = LpObjective(name='minimize_cpm',
expression={x: 998},
constant=8,
sense=Maximize)
rhs = LpExpression('rhs', {x: 1})
lhs = LpExpression('lhs', {}, -2)
constraint = LpConstraint(rhs, 'leq', lhs, 'constraint', True, 100)
problem.add_constraint(constraint)
problem.set_objective(objective)
buffer = StringIO()
problem.write_lp(buffer)
flipy_string = buffer.getvalue()
assert flipy_string == '\\* test_problem *\\\nMaximize\nminimize_cpm: 998 x - 100 constraint_slack_variable + 8\nSubject To\nconstraint: - constraint_slack_variable + x <= -2\nBounds\nx <= 10\nEnd'
def test_write_long(self, problem, x):
a = LpVariable('a', low_bound=0, up_bound=10, var_type=VarType.Integer)
b = LpVariable('b', low_bound=0, up_bound=10, var_type=VarType.Integer)
c = LpVariable('c', low_bound=0, up_bound=10, var_type=VarType.Integer)
d = LpVariable('d', low_bound=0, up_bound=10, var_type=VarType.Integer)
e = LpVariable('e', var_type=VarType.Binary)
f = LpVariable('f', var_type=VarType.Binary)
g = LpVariable('g', var_type=VarType.Binary)
h = LpVariable('h', var_type=VarType.Binary)
vars = [a, b, c, d, e, f, g, h]
# make sure objective is long enough to test the line break
objective = LpObjective(name='minimize_cpm',
expression={v: 3.1415926535
for v in vars},
constant=8)
rhs = LpExpression('rhs', {a: 1000, b: 1000, c: 1000, d: 1000})
lhs = LpExpression('lhs', {}, -2)
constraint = LpConstraint(rhs, 'geq', lhs, 'constraint')
problem.add_constraint(constraint)
problem.set_objective(objective)
buffer = StringIO()
problem.write_lp(buffer)
lp_str = buffer.getvalue()
assert lp_str.split('\n') == [
'\\* test_problem *\\', 'Minimize',
'minimize_cpm: 3.1415926535 a + 3.1415926535 b + 3.1415926535 c + 3.1415926535 d',
'+ 3.1415926535 e + 3.1415926535 f + 3.1415926535 g + 3.1415926535 h + 8',
'Subject To',
'constraint: 1000 a + 1000 b + 1000 c + 1000 d >= -2', 'Bounds',
'0 <= a <= 10', '0 <= b <= 10', '0 <= c <= 10', '0 <= d <= 10',
'0 <= e <= 1', '0 <= f <= 1', '0 <= g <= 1', '0 <= h <= 1',
'Generals', 'a', 'b', 'c', 'd', 'Binaries', 'e', 'f', 'g', 'h',
'End'
]
def test_invalid_slack(self, lhs):
with pytest.raises(ValueError) as e:
LpConstraint(lhs, 'leq', slack='invalid')
assert 'slack' in e.message.lower()
def test_init_no_rhs(self, lhs):
lp_constraint = LpConstraint(lhs, 'leq')
assert lp_constraint.rhs == LpExpression()
def lp_constraint_with_slack(lhs, rhs):
return LpConstraint(lhs, 'leq', rhs, 'test_constraint', True, 10.)
def lp_constraint(lhs, rhs):
return LpConstraint(lhs, 'leq', rhs, 'test_constraint')
def read(cls, obj: Union[str, IO, TextIO, io.StringIO]) -> LpProblem:
""" Reads in an LP file and parse it into a flipy.LpProblem object
Raises
------
ValueError
If `obj` is unreadable and is not a LP string
Parameters
----------
obj: str or buffer
Returns
-------
LpProblem
Parsed LpProblem based on the LP file
"""
if hasattr(obj, 'read'):
content = obj.read()
elif isinstance(obj, (str, bytes)):
content = obj
try:
if os.path.isfile(content):
with open(content, "rb") as f:
content = f.read()
except (TypeError, ValueError):
pass
else:
raise ValueError("Cannot read object of type %r" %
type(obj).__name__)
content = content.strip()
problem_name = cls._find_problem_name(content)
is_maximize, sections = cls._split_content_by_sections(
cls._remove_comments(content))
obj_name, obj_expr, obj_coeff = cls._parse_named_expression(
sections['objective'])
constraints = cls._parse_constraints(
sections['constraints']) if 'constraints' in sections else []
bounds = cls._parse_bounds(
sections['bounds']) if 'bounds' in sections else []
generals = cls._parse_generals(
sections['generals']) if 'generals' in sections else []
binaries = cls._parse_binaries(
sections['binaries']) if 'binaries' in sections else []
lp_variables = {}
lp_objective = LpObjective(obj_name,
constant=obj_coeff,
sense=Maximize if is_maximize else Minimize)
for obj_var_name, obj_coeff in obj_expr.items():
obj_var = cls._find_variable(lp_variables, obj_var_name)
lp_objective.expr[obj_var] = obj_coeff
lp_constraints = []
for constraint in constraints:
lhs_expr = LpExpression()
for var_name, cons_var_coeff in constraint['lhs'].items():
var = cls._find_variable(lp_variables, var_name)
lhs_expr.expr[var] = cons_var_coeff
lhs_expr.const = constraint['lhs_const']
rhs_expr = LpExpression()
for var_name, cons_var_coeff in constraint['rhs'].items():
var = cls._find_variable(lp_variables, var_name)
rhs_expr.expr[var] = cons_var_coeff
rhs_expr.const = constraint['rhs_const']
lp_constraints.append(
LpConstraint(lhs_expr,
constraint['sense'],
rhs_expr,
name=constraint['name']))
cls._parse_variables(lp_variables, bounds, generals, binaries)
return LpProblem(problem_name,
lp_objective=lp_objective,
lp_constraints=lp_constraints)
def test_invalid_slack_penalty(self, lhs):
with pytest.raises(ValueError) as e:
LpConstraint(lhs, 'leq', slack_penalty=-1)
assert 'slack penalty' in e.message.lower()
