X-Git-Url: https://scm.cri.ensmp.fr/git/linpy.git/blobdiff_plain/f3795845e035704393ac7c2efdeb061df71a9b67..a93fd1cb792ef6dafaeb2599823256241c061cd3:/linpy/polyhedra.py diff --git a/linpy/polyhedra.py b/linpy/polyhedra.py index 543e673..b88cfd1 100644 --- a/linpy/polyhedra.py +++ b/linpy/polyhedra.py @@ -87,22 +87,20 @@ class Polyhedron(Domain): if inequalities is not None: raise TypeError('too many arguments') return equalities.aspolyhedron() - if equalities is None: - equalities = [] - else: - for i, equality in enumerate(equalities): + sc_equalities = [] + if equalities is not None: + for equality in equalities: if not isinstance(equality, LinExpr): raise TypeError('equalities must be linear expressions') - equalities[i] = equality.scaleint() - if inequalities is None: - inequalities = [] - else: - for i, inequality in enumerate(inequalities): + sc_equalities.append(equality.scaleint()) + sc_inequalities = [] + if inequalities is not None: + for inequality in inequalities: if not isinstance(inequality, LinExpr): raise TypeError('inequalities must be linear expressions') - inequalities[i] = inequality.scaleint() - symbols = cls._xsymbols(equalities + inequalities) - islbset = cls._toislbasicset(equalities, inequalities, symbols) + sc_inequalities.append(inequality.scaleint()) + symbols = cls._xsymbols(sc_equalities + sc_inequalities) + islbset = cls._toislbasicset(sc_equalities, sc_inequalities, symbols) return cls._fromislbasicset(islbset, symbols) @property @@ -146,6 +144,15 @@ class Polyhedron(Domain): def aspolyhedron(self): return self + def convex_union(self, *others): + """ + Return the convex union of two or more polyhedra. + """ + for other in others: + if not isinstance(other, Polyhedron): + raise TypeError('arguments must be Polyhedron instances') + return Polyhedron(self.union(*others)) + def __contains__(self, point): if not isinstance(point, Point): raise TypeError('point must be a Point instance') @@ -166,7 +173,11 @@ class Polyhedron(Domain): for inequality in self.inequalities] return Polyhedron(equalities, inequalities) - def _asinequalities(self): + def asinequalities(self): + """ + Express the polyhedron using inequalities, given as a list of + expressions greater or equal to 0. + """ inequalities = list(self.equalities) inequalities.extend([-expression for expression in self.equalities]) inequalities.extend(self.inequalities) @@ -175,11 +186,14 @@ class Polyhedron(Domain): def widen(self, other): """ Compute the standard widening of two polyhedra, à la Halbwachs. + + In its current implementation, this method is slow and should not be + used on large polyhedra. """ if not isinstance(other, Polyhedron): - raise ValueError('argument must be a Polyhedron instance') - inequalities1 = self._asinequalities() - inequalities2 = other._asinequalities() + raise TypeError('argument must be a Polyhedron instance') + inequalities1 = self.asinequalities() + inequalities2 = other.asinequalities() inequalities = [] for inequality1 in inequalities1: if other <= Polyhedron(inequalities=[inequality1]): @@ -305,8 +319,6 @@ class EmptyType(Polyhedron): The empty polyhedron, whose set of constraints is not satisfiable. """ - __slots__ = Polyhedron.__slots__ - def __new__(cls): self = object().__new__(cls) self._equalities = (Rational(1),) @@ -335,8 +347,6 @@ class UniverseType(Polyhedron): i.e. is empty. """ - __slots__ = Polyhedron.__slots__ - def __new__(cls): self = object().__new__(cls) self._equalities = () @@ -402,15 +412,15 @@ def Ne(left, right): return ~Eq(left, right) @_polymorphic -def Gt(left, right): +def Ge(left, right): """ - Create the polyhedron with constraints expr1 > expr2 > expr3 ... + Create the polyhedron with constraints expr1 >= expr2 >= expr3 ... """ - return Polyhedron([], [left - right - 1]) + return Polyhedron([], [left - right]) @_polymorphic -def Ge(left, right): +def Gt(left, right): """ - Create the polyhedron with constraints expr1 >= expr2 >= expr3 ... + Create the polyhedron with constraints expr1 > expr2 > expr3 ... """ - return Polyhedron([], [left - right]) + return Polyhedron([], [left - right - 1])