def test_univariate_concave(self, problem, constraint_name):
ctx = ProblemContext(problem)
r = UnivariateConcaveExpressionRelaxation()
constraint_expr = problem.constraint(constraint_name).root_expr
ctx.set_convexity(constraint_expr, Convexity.Concave)
assert r.can_relax(problem, constraint_expr, ctx)
result = r.relax(problem, constraint_expr, ctx)
assert result.constraints == []
def test_quadratic_expression(self, problem):
ctx = ProblemContext(problem)
r = ConvexExpressionRelaxation()
constraint_expr = problem.constraint('c0').root_expr
ctx.set_convexity(constraint_expr, Convexity.Unknown)
assert r.can_relax(problem, constraint_expr, ctx)
result = r.relax(problem, constraint_expr, ctx)
expr = result.expression
assert expr.expression_type == ExpressionType.Quadratic
assert len(expr.terms) == 2
for term in expr.terms:
assert term.var1 == term.var2
assert term.coefficient == 2.0 or term.coefficient == 4.0
assert result.constraints == []
def test_sum_of_convex_expressions(self, problem):
ctx = ProblemContext(problem)
r = ConvexExpressionRelaxation()
constraint_expr = problem.objective.root_expr
ctx.set_convexity(constraint_expr, Convexity.Convex)
assert r.can_relax(problem, constraint_expr, ctx)
result = r.relax(problem, constraint_expr, ctx)
assert len(result.expression.children) == 2
assert result.expression.expression_type == ExpressionType.Sum
a, b = result.expression.children
assert a.expression_type == ExpressionType.UnaryFunction
assert b.expression_type == ExpressionType.UnaryFunction
assert result.constraints == []