Fix Polyhedron.isempty()
[linpy.git] / pypol / linear.py
index 348294c..5f3c559 100644 (file)
@@ -4,8 +4,8 @@ import numbers
 
 from fractions import Fraction, gcd
 
-from . import isl, islhelper
-from .isl import libisl, Context, BasicSet
+from . import isl
+from .isl import libisl
 
 
 __all__ = [
@@ -42,6 +42,9 @@ def _polymorphic_operator(func):
     return wrapper
 
 
+_main_ctx = isl.Context()
+
+
 class Expression:
     """
     This class implements linear expressions.
@@ -69,15 +72,17 @@ class Expression:
         if not isinstance(constant, numbers.Rational):
             raise TypeError('constant must be a rational number')
         self._constant = constant
+        self._symbols = tuple(sorted(self._coefficients))
+        self._dimension = len(self._symbols)
         return self
 
-
+    @property
     def symbols(self):
-        yield from sorted(self._coefficients)
+        return self._symbols
 
     @property
     def dimension(self):
-        return len(list(self.symbols()))
+        return self._dimension
 
     def coefficient(self, symbol):
         if isinstance(symbol, Expression) and symbol.issymbol():
@@ -91,9 +96,8 @@ class Expression:
 
     __getitem__ = coefficient
 
-    @property
     def coefficients(self):
-        for symbol in self.symbols():
+        for symbol in self.symbols:
             yield symbol, self.coefficient(symbol)
 
     @property
@@ -104,19 +108,20 @@ class Expression:
         return len(self._coefficients) == 0
 
     def values(self):
-        for symbol in self.symbols():
+        for symbol in self.symbols:
             yield self.coefficient(symbol)
         yield self.constant
 
     def values_int(self):
-        for symbol in self.symbols():
+        for symbol in self.symbols:
             return self.coefficient(symbol)
         return int(self.constant)
 
+    @property
     def symbol(self):
         if not self.issymbol():
             raise ValueError('not a symbol: {}'.format(self))
-        for symbol in self.symbols():
+        for symbol in self.symbols:
             return symbol
 
     def issymbol(self):
@@ -133,8 +138,8 @@ class Expression:
 
     @_polymorphic_method
     def __add__(self, other):
-        coefficients = dict(self.coefficients)
-        for symbol, coefficient in other.coefficients:
+        coefficients = dict(self.coefficients())
+        for symbol, coefficient in other.coefficients():
             if symbol in coefficients:
                 coefficients[symbol] += coefficient
             else:
@@ -146,8 +151,8 @@ class Expression:
 
     @_polymorphic_method
     def __sub__(self, other):
-        coefficients = dict(self.coefficients)
-        for symbol, coefficient in other.coefficients:
+        coefficients = dict(self.coefficients())
+        for symbol, coefficient in other.coefficients():
             if symbol in coefficients:
                 coefficients[symbol] -= coefficient
             else:
@@ -161,7 +166,7 @@ class Expression:
     @_polymorphic_method
     def __mul__(self, other):
         if other.isconstant():
-            coefficients = dict(self.coefficients)
+            coefficients = dict(self.coefficients())
             for symbol in coefficients:
                 coefficients[symbol] *= other.constant
             constant = self.constant * other.constant
@@ -199,7 +204,6 @@ class Expression:
 
     def __str__(self):
         string = ''
-        symbols = sorted(self.symbols())
         i = 0
         for symbol in symbols:
             coefficient = self[symbol]
@@ -244,7 +248,7 @@ class Expression:
 
     def __repr__(self):
         string = '{}({{'.format(self.__class__.__name__)
-        for i, (symbol, coefficient) in enumerate(self.coefficients):
+        for i, (symbol, coefficient) in enumerate(self.coefficients()):
             if i != 0:
                 string += ', '
             string += '{!r}: {!r}'.format(symbol, coefficient)
@@ -266,30 +270,30 @@ class Expression:
     def __hash__(self):
         return hash((self._coefficients, self._constant))
 
-    def _canonify(self):
+    def _toint(self):
         lcm = functools.reduce(lambda a, b: a*b // gcd(a, b),
                 [value.denominator for value in self.values()])
         return self * lcm
 
     @_polymorphic_method
     def _eq(self, other):
-        return Polyhedron(equalities=[(self - other)._canonify()])
+        return Polyhedron(equalities=[(self - other)._toint()])
 
     @_polymorphic_method
     def __le__(self, other):
-        return Polyhedron(inequalities=[(other - self)._canonify()])
+        return Polyhedron(inequalities=[(other - self)._toint()])
 
     @_polymorphic_method
     def __lt__(self, other):
-        return Polyhedron(inequalities=[(other - self)._canonify() - 1])
+        return Polyhedron(inequalities=[(other - self)._toint() - 1])
 
     @_polymorphic_method
     def __ge__(self, other):
-        return Polyhedron(inequalities=[(self - other)._canonify()])
+        return Polyhedron(inequalities=[(self - other)._toint()])
 
     @_polymorphic_method
     def __gt__(self, other):
-        return Polyhedron(inequalities=[(self - other)._canonify() - 1])
+        return Polyhedron(inequalities=[(self - other)._toint() - 1])
 
 
 def constant(numerator=0, denominator=None):
@@ -349,6 +353,7 @@ class Polyhedron:
                         raise TypeError('non-integer constraint: '
                                 '{} == 0'.format(constraint))
                 self._equalities.append(constraint)
+        self._equalities = tuple(self._equalities)
         self._inequalities = []
         if inequalities is not None:
             for constraint in inequalities:
@@ -357,46 +362,36 @@ class Polyhedron:
                         raise TypeError('non-integer constraint: '
                                 '{} <= 0'.format(constraint))
                 self._inequalities.append(constraint)
+        self._inequalities = tuple(self._inequalities)
+        self._constraints = self._equalities + self._inequalities
+        self._symbols = set()
+        for constraint in self._constraints:
+            self.symbols.update(constraint.symbols)
+        self._symbols = tuple(sorted(self._symbols))
         return self
 
     @property
     def equalities(self):
-        yield from self._equalities
+        return self._equalities
 
     @property
     def inequalities(self):
-        yield from self._inequalities
+        return self._inequalities
 
     @property
-    def constant(self):
-        return self._constant
-
-    def isconstant(self):
-        return len(self._coefficients) == 0
-
-    def isempty(self):
-        return bool(libisl.isl_basic_set_is_empty(self._bset))
-
     def constraints(self):
-        yield from self.equalities
-        yield from self.inequalities
+        return self._constraints
 
+    @property
     def symbols(self):
-        s = set()
-        for constraint in self.constraints():
-            s.update(constraint.symbols())
-        return sorted(s)
+        return self._symbols
 
     @property
     def dimension(self):
-        return len(self.symbols())
+        return len(self.symbols)
 
     def __bool__(self):
-        # return false if the polyhedron is empty, true otherwise
-        if self._equalities or self._inequalities:
-            return False
-        else:
-            return True
+        return not self.is_empty()
 
     def __contains__(self, value):
         # is the value in the polyhedron?
@@ -405,11 +400,12 @@ class Polyhedron:
     def __eq__(self, other):
         raise NotImplementedError
 
-    def is_empty(self):
-        return
+    def isempty(self):
+        bset = self._to_isl()
+        return bool(libisl.isl_basic_set_is_empty(bset))
 
     def isuniverse(self):
-        return self == universe
+        raise NotImplementedError
 
     def isdisjoint(self, other):
         # return true if the polyhedron has no elements in common with other
@@ -426,11 +422,6 @@ class Polyhedron:
 
     def issuperset(self, other):
         # test whether every element in other is in the polyhedron
-        for value in other:
-            if value == self.constraints():
-                return True
-            else:
-                return False
         raise NotImplementedError
 
     def __ge__(self, other):
@@ -489,17 +480,16 @@ class Polyhedron:
         raise NotImplementedError
 
     def _symbolunion(self, *others):
-        symbols = set(self.symbols())
+        symbols = set(self.symbols)
         for other in others:
-            symbols.update(other.symbols())
+            symbols.update(other.symbols)
         return sorted(symbols)
 
     def _to_isl(self, symbols=None):
         if symbols is None:
-            symbols = self.symbols()
+            symbols = self.symbols
         num_coefficients = len(symbols)
-        ctx = Context()
-        space = libisl.isl_space_set_alloc(ctx, 0, num_coefficients)
+        space = libisl.isl_space_set_alloc(_main_ctx, 0, num_coefficients)
         bset = libisl.isl_basic_set_universe(libisl.isl_space_copy(space))
         ls = libisl.isl_local_space_from_space(space)
         ceq = libisl.isl_equality_alloc(libisl.isl_local_space_copy(ls))
@@ -507,49 +497,57 @@ class Polyhedron:
         '''if there are equalities/inequalities, take each constant and coefficient and add as a constraint to the basic set'''
         if list(self.equalities): #check if any equalities exist
             for eq in self.equalities:
-                coeff_eq = dict(eq.coefficients)
+                coeff_eq = dict(eq.coefficients())
                 if eq.constant:
                     value = eq.constant
                     ceq = libisl.isl_constraint_set_constant_si(ceq, value)
                 for eq in coeff_eq:
                     num = coeff_eq.get(eq)
                     iden = symbols.index(eq)
-                    ceq = libisl.isl_constraint_set_coefficient_si(ceq, islhelper.isl_dim_set, iden, num)  #use 3 for type isl_dim_set
+                    ceq = libisl.isl_constraint_set_coefficient_si(ceq, libisl.isl_dim_set, iden, num)  #use 3 for type isl_dim_set
             bset = libisl.isl_basic_set_add_constraint(bset, ceq)
         if list(self.inequalities): #check if any inequalities exist
             for ineq in self.inequalities:
-                coeff_in = dict(ineq.coefficients)
+                coeff_in = dict(ineq.coefficients())
                 if ineq.constant:
                     value = ineq.constant
                     cin = libisl.isl_constraint_set_constant_si(cin, value)
                 for ineq in coeff_in:
                     num = coeff_in.get(ineq)
                     iden = symbols.index(ineq)
-                    cin = libisl.isl_constraint_set_coefficient_si(cin, islhelper.isl_dim_set, iden, num)  #use 3 for type isl_dim_set
+                    cin = libisl.isl_constraint_set_coefficient_si(cin, libisl.isl_dim_set, iden, num)  #use 3 for type isl_dim_set
             bset = libisl.isl_basic_set_add_constraint(bset, cin)
-        bset = BasicSet(bset)
+        bset = isl.BasicSet(bset)
         return bset
 
-    def from_isl(self, bset):
+    @classmethod
+    def _from_isl(cls, bset):
         '''takes basic set in isl form and puts back into python version of polyhedron
         isl example code gives isl form as:
             "{[i] : exists (a : i = 2a and i >= 10 and i <= 42)}")
             our printer is giving form as:
             b'{ [i0] : 1 = 0 }' '''
+        raise NotImplementedError
+        equalities = ...
+        inequalities = ...
+        return cls(equalities, inequalities)
         #bset = self
-        if self._equalities:
-            constraints = libisl.isl_basic_set_equalities_matrix(bset, 3)
-        elif self._inequalities:
-            constraints = libisl.isl_basic_set_inequalities_matrix(bset, 3)
-        print(constraints)
-        return constraints
+        if self._equalities:
+            constraints = libisl.isl_basic_set_equalities_matrix(bset, 3)
+        elif self._inequalities:
+            constraints = libisl.isl_basic_set_inequalities_matrix(bset, 3)
+        print(constraints)
+        return constraints
 
 empty = None #eq(0,1)
 universe = None #Polyhedron()
 
+
 if __name__ == '__main__':
     ex1 = Expression(coefficients={'a': 1, 'x': 2}, constant=2)
     ex2 = Expression(coefficients={'a': 3  , 'b': 2}, constant=3)
     p = Polyhedron(inequalities=[ex1, ex2])
     bs = p._to_isl()
     print(bs)
+    print('empty ?', p.isempty())
+    print('empty ?', eq(0, 1).isempty())