Added Symbol values function to PQC (tensorflow#177)

* Added symbol_values function to PQC. * strange format. Co-authored-by: Michael Broughton <[email protected]>
maneeshs · Mar 30, 2020 · 46aa11b · 46aa11b
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diff --git a/tensorflow_quantum/python/layers/high_level/pqc.py b/tensorflow_quantum/python/layers/high_level/pqc.py
@@ -270,6 +270,15 @@ def symbols(self):
         """
         return [sympy.Symbol(x) for x in self._symbols_list]
 
+    def symbol_values(self):
+        """Returns a Python `dict` containing symbol name, value pairs.
+
+        Returns:
+            Python `dict` with `str` keys and `float` values representing
+                the current symbol values.
+        """
+        return dict(zip(self.symbols, self.get_weights()[0]))
+
     def build(self, input_shape):
         """Keras build function."""
         super().build(input_shape)

diff --git a/tensorflow_quantum/python/layers/high_level/pqc_test.py b/tensorflow_quantum/python/layers/high_level/pqc_test.py
@@ -170,6 +170,22 @@ def test_pqc_symbols_property(self):
         layer = pqc.PQC(test_circuit, cirq.Z(bit))
         self.assertEqual(layer.symbols, [a, b, c, d])
 
+    def test_pqc_symbol_values(self):
+        """Test that PQC symbol_values returns the correct key value pairs."""
+        c, b, a, d = sympy.symbols('c b a d')
+        bit = cirq.GridQubit(0, 0)
+        test_circuit = cirq.Circuit(
+            cirq.H(bit)**a,
+            cirq.Z(bit)**b,
+            cirq.X(bit)**d,
+            cirq.Y(bit)**c)
+        init_vals = [1, 2, 3, 4]
+        layer = pqc.PQC(test_circuit,
+                        cirq.Z(bit),
+                        initializer=tf.constant_initializer(init_vals))
+        expected_vals = dict(zip([a, b, c, d], init_vals))
+        self.assertAllClose(layer.symbol_values(), expected_vals)
+
     @parameterized.parameters(
         list(
             util.kwargs_cartesian_product(backend=[None, cirq.Simulator()],