Issues/302 sympy free symbols

qctoolkit/expressions.py

@@ -7,13 +7,14 @@
 import warnings
 import functools
 import array
+import itertools
 
 import sympy
 import numpy
 
 from qctoolkit.serialization import AnonymousSerializable
 from qctoolkit.utils.sympy import sympify, to_numpy, recursive_substitution, evaluate_lambdified,\
-    get_most_simple_representation
+    get_most_simple_representation, get_variables
 
 __all__ = ["Expression", "ExpressionVariableMissingException", "ExpressionScalar", "ExpressionVector"]
 
@@ -125,9 +126,7 @@ def __init__(self, expression_vector: Sequence):
         if isinstance(expression_vector, sympy.NDimArray):
             expression_vector = to_numpy(expression_vector)
         self._expression_vector = self.sympify_vector(expression_vector)
-        variables = {str(x)
-                     for expr in self._expression_vector.ravel()
-                     for x in expr.free_symbols}
+        variables = set(itertools.chain.from_iterable(map(get_variables, self._expression_vector.flat)))
         self._variables = tuple(variables)
 
     @property
@@ -220,7 +219,7 @@ def __init__(self, ex: Union[str, Number, sympy.Expr]) -> None:
             self._original_expression = ex
             self._sympified_expression = sympify(ex)
 
-        self._variables = tuple(str(var) for var in self._sympified_expression.free_symbols)
+        self._variables = get_variables(self._sympified_expression)
 
     @property
     def underlying_expression(self) -> sympy.Expr:

qctoolkit/utils/sympy.py

@@ -9,7 +9,8 @@
 import numpy
 
 
-__all__ = ["sympify", "substitute_with_eval", "to_numpy"]
+__all__ = ["sympify", "substitute_with_eval", "to_numpy", "get_variables", "get_free_symbols", "recursive_substitution",
+           "evaluate_lambdified", "get_most_simple_representation"]
 
 
 Sympifyable = Union[str, Number, sympy.Expr, numpy.str_]
@@ -119,13 +120,23 @@ def get_most_simple_representation(expression: sympy.Expr) -> Union[str, int, fl
         return str(expression)
 
 
+def get_free_symbols(expression: sympy.Expr) -> Sequence[sympy.Symbol]:
+    return tuple(symbol
+                 for symbol in expression.free_symbols
+                 if not isinstance(symbol, sympy.Indexed))
+
+
+def get_variables(expression: sympy.Expr) -> Sequence[str]:
+    return tuple(map(str, get_free_symbols(expression)))
+
+
 def substitute_with_eval(expression: sympy.Expr,
                          substitutions: Dict[str, Union[sympy.Expr, numpy.ndarray, str]]) -> sympy.Expr:
     """Substitutes only sympy.Symbols. Workaround for numpy like array behaviour. ~Factor 3 slower compared to subs"""
     substitutions = {k: v if isinstance(v, sympy.Expr) else sympify(v)
                      for k, v in substitutions.items()}
 
-    for symbol in expression.free_symbols:
+    for symbol in get_free_symbols(expression):
         symbol_name = str(symbol)
         if symbol_name not in substitutions:
             substitutions[symbol_name] = symbol
@@ -146,14 +157,14 @@ def _recursive_substitution(expression: sympy.Expr,
         func = numpy_compatible_mul
     else:
         func = expression.func
-    substitutions = {s: substitutions.get(s, s) for s in expression.free_symbols}
+    substitutions = {s: substitutions.get(s, s) for s in get_free_symbols(expression)}
     return func(*(_recursive_substitution(arg, substitutions) for arg in expression.args))
 
 
 def recursive_substitution(expression: sympy.Expr,
                            substitutions: Dict[str, Union[sympy.Expr, numpy.ndarray, str]]) -> sympy.Expr:
     substitutions = {sympy.Symbol(k): sympify(v) for k, v in substitutions.items()}
-    for s in expression.free_symbols:
+    for s in get_free_symbols(expression):
         substitutions.setdefault(s, s)
     return _recursive_substitution(expression, substitutions)
 

requirements.txt

@@ -0,0 +1 @@
+.

setup.py

@@ -21,7 +21,7 @@
       package_dir={'qctoolkit': 'qctoolkit'},
       packages=packages,
       tests_require=['pytest'],
-      install_requires=['sympy==1.1.1', 'numpy'] + requires_typing,
+      install_requires=['sympy>=1.1.1', 'numpy'] + requires_typing,
       extras_require={
           'testing': ['pytest'],
           'plotting': ['matplotlib'],

tests/expression_tests.py

@@ -201,6 +201,12 @@ def test_variables(self) -> None:
         received = sorted(e.variables)
         self.assertEqual(expected, received)
 
+    def test_variables_indexed(self):
+        e = ExpressionScalar('a[i] * c')
+        expected = sorted(['a', 'i', 'c'])
+        received = sorted(e.variables)
+        self.assertEqual(expected, received)
+
     def test_evaluate_variable_missing(self) -> None:
         e = ExpressionScalar('a * b + c')
         params = {

tests/utils/sympy_tests.py

@@ -13,7 +13,8 @@
 a_ = IndexedBase(a)
 b_ = IndexedBase(b)
 
-from qctoolkit.utils.sympy import sympify as qc_sympify, substitute_with_eval, recursive_substitution, Len, evaluate_lambdified, evaluate_compiled, get_most_simple_representation
+from qctoolkit.utils.sympy import sympify as qc_sympify, substitute_with_eval, recursive_substitution, Len,\
+    evaluate_lambdified, evaluate_compiled, get_most_simple_representation, get_variables, get_free_symbols
 
 
 ################################################### SUBSTITUTION #######################################################
@@ -214,15 +215,34 @@ def substitute(self, expression: sympy.Expr, substitutions: dict):
         return recursive_substitution(expression, substitutions).doit()
 
 
+class GetFreeSymbolsTests(TestCase):
+    def assert_symbol_sets_equal(self, expected, actual):
+        self.assertEqual(len(expected), len(actual))
+        self.assertEqual(set(expected), set(actual))
+
+    def test_get_free_symbols(self):
+        expr = a * b / 5
+        self.assert_symbol_sets_equal([a, b], get_free_symbols(expr))
+
+    def test_get_free_symbols_indexed(self):
+        expr = a_[i] * IndexedBase(a*b)[j]
+        self.assert_symbol_sets_equal({a, b, i, j}, set(get_free_symbols(expr)))
+
+    def test_get_variables(self):
+        expr = a * b / 5
+        self.assertEqual({'a', 'b'}, set(get_variables(expr)))
+
+    def test_get_variables_indexed(self):
+        expr = a_[i] * IndexedBase(a*b)[j]
+        self.assertEqual({'a', 'b', 'i', 'j'}, set(get_variables(expr)))
+
+
 class EvaluationTests(TestCase):
     def evaluate(self, expression: Union[sympy.Expr, np.ndarray], parameters):
-        def get_variables(expr: sympy.Expr):
-            return {str(s) for s in expr.free_symbols}
         if isinstance(expression, np.ndarray):
-            vectorized = np.vectorize(get_variables)
-            get_variables = lambda expr: set.union(*vectorized(expr))
-
-        variables = get_variables(expression)
+            variables = set.union(*map(set, map(get_variables, expression.flat)))
+        else:
+            variables = get_variables(expression)
         return evaluate_lambdified(expression, variables=list(variables), parameters=parameters, lambdified=None)[0]
 
     def test_eval_simple(self):