Better tolerances for gate decompositions

qiskit/circuit/quantumcircuit.py

@@ -1881,12 +1881,10 @@ def global_phase(self, angle):
         if isinstance(angle, ParameterExpression) and angle.parameters:
             self._global_phase = angle
         else:
-            # Set the phase to the [-2 * pi, 2 * pi] interval
+            # Set the phase to the [0, 2π) interval
             angle = float(angle)
             if not angle:
                 self._global_phase = 0
-            elif angle < 0:
-                self._global_phase = angle % (-2 * np.pi)
             else:
                 self._global_phase = angle % (2 * np.pi)
 

qiskit/dagcircuit/dagcircuit.py

@@ -889,10 +889,11 @@ def __eq__(self, other):
         # Try to convert to float, but in case of unbound ParameterExpressions
         # a TypeError will be raise, fallback to normal equality in those
         # cases
+
         try:
             self_phase = float(self.global_phase)
             other_phase = float(other.global_phase)
-            if not np.isclose(self_phase, other_phase):
+            if (self_phase - other_phase + np.pi) % (2 * np.pi) - np.pi > 1.E-10:  # XXX: tolerance
                 return False
         except TypeError:
             if self.global_phase != other.global_phase:
@@ -916,7 +917,6 @@ def __eq__(self, other):
                               for regname, reg in other.qregs.items()]
         other_creg_indices = [(regname, [other_bit_indices[bit] for bit in reg])
                               for regname, reg in other.cregs.items()]
-
         if (
                 self_qreg_indices != other_qreg_indices
                 or self_creg_indices != other_creg_indices

test/python/circuit/test_unitary.py

@@ -258,7 +258,10 @@ def test_qasm_2q_unitary(self):
         qr = QuantumRegister(2, 'q0')
         cr = ClassicalRegister(1, 'c0')
         qc = QuantumCircuit(qr, cr)
-        matrix = numpy.eye(4)
+        matrix = numpy.asarray([[0, 0, 0, 1],
+                                [0, 0, 1, 0],
+                                [0, 1, 0, 0],
+                                [1, 0, 0, 0]])
         unitary_gate = UnitaryGate(matrix, label="custom_gate")
 
         qc.x(qr[0])
@@ -271,8 +274,8 @@ def test_qasm_2q_unitary(self):
                         "creg c0[1];\n" \
                         "x q0[0];\n" \
                         "gate custom_gate p0,p1 {\n" \
-                        "\tu3(0,0,0) p0;\n" \
-                        "\tu3(0,0,0) p1;\n" \
+                        "\tu3(pi,-pi/2,pi/2) p0;\n" \
+                        "\tu3(pi,pi/2,-pi/2) p1;\n" \
                         "}\n" \
                         "custom_gate q0[0],q0[1];\n" \
                         "custom_gate q0[1],q0[0];\n"

test/python/compiler/test_transpiler.py

@@ -541,7 +541,8 @@ def test_optimize_to_nothing(self):
                           basis_gates=['u3', 'u2', 'u1', 'cx'])
 
         expected = QuantumCircuit(QuantumRegister(2, 'q'), global_phase=-np.pi/2)
-        self.assertEqual(after, expected)
+        msg = f"after:\n{after}\nexpected:\n{expected}"
+        self.assertEqual(after, expected, msg=msg)
 
     def test_pass_manager_empty(self):
         """Test passing an empty PassManager() to the transpiler.
@@ -995,12 +996,12 @@ def test_no_infinite_loop(self, optimization_level):
         # for the second and third RZ gates in the U3 decomposition.
         expected = QuantumCircuit(1, global_phase=-np.pi/2 - 0.5 * (0.2 + np.pi) - 0.5 * 3 * np.pi)
         expected.sx(0)
-        expected.p(np.pi + 0.2, 0)
+        expected.p(-np.pi + 0.2, 0)
         expected.sx(0)
-        expected.p(np.pi, 0)
+        expected.p(-np.pi, 0)
 
-        error_message = "\nOutput circuit:\n%s\nExpected circuit:\n%s" % (
-            str(out), str(expected))
+        error_message = (f"\nOutput circuit:\n{out!s}\n{Operator(out).data}\n"
+                         f"Expected circuit:\n{expected!s}\n{Operator(expected).data}")
         self.assertEqual(out, expected, error_message)
 
     @data(0, 1, 2, 3)

test/python/quantum_info/states/test_statevector.py

@@ -925,7 +925,7 @@ def test_global_phase(self):
         qc2 = transpile(qc, basis_gates=['p'])
         sv = Statevector.from_instruction(qc2)
         expected = np.array([0.96891242-0.24740396j, 0])
-        self.assertEqual(float(qc2.global_phase), -1/4)
+        self.assertEqual(float(qc2.global_phase), 2*np.pi - 0.25)
         self.assertEqual(sv, Statevector(expected))
 
     def test_reverse_qargs(self):

test/python/transpiler/test_basis_translator.py

@@ -775,5 +775,6 @@ def test_global_phase(self):
         expected.global_phase = circ_angle - gate_angle / 2
         expected_dag = circuit_to_dag(expected)
         self.assertEqual(out_dag, expected_dag)
-        self.assertEqual(float(out_dag.global_phase), float(expected_dag.global_phase))
+        self.assertAlmostEqual(float(out_dag.global_phase), float(expected_dag.global_phase),
+                               places=14)
         self.assertEqual(Operator(dag_to_circuit(out_dag)), Operator(expected))

test/python/transpiler/test_commutative_cancellation.py

@@ -417,7 +417,8 @@ def test_commutative_circuit3(self):
         expected.append(RZGate(np.pi * 2 / 3), [qr[3]])
         expected.cx(qr[2], qr[1])
 
-        self.assertEqual(expected, new_circuit)
+        self.assertEqual(expected, new_circuit,
+                         msg=f'expected:\n{expected}\nnew_circuit:\n{new_circuit}')
 
     def test_cnot_cascade(self):
         """

test/python/transpiler/test_optimize_1q_decomposition.py

@@ -346,7 +346,7 @@ def test_euler_decomposition_worse(self):
         result = passmanager.run(circuit)
         # decomposition of circuit will result in 3 gates instead of 2
         # assert optimization pass doesn't use it.
-        self.assertEqual(result, circuit)
+        self.assertEqual(circuit, result, f"Circuit:\n{circuit}\nResult:\n{result}")
 
     def test_optimize_u_to_phase_gate(self):
         """U(0, 0, pi/4) ->  p(pi/4). Basis [p, sx]."""
@@ -363,7 +363,8 @@ def test_optimize_u_to_phase_gate(self):
         passmanager.append(Optimize1qGatesDecomposition(basis))
         result = passmanager.run(circuit)
 
-        self.assertEqual(expected, result)
+        msg = f"expected:\n{expected}\nresult:\n{result}"
+        self.assertEqual(expected, result, msg=msg)
 
     def test_optimize_u_to_p_sx_p(self):
         """U(pi/2, 0, pi/4) ->  p(-pi/4)-sx-p(p/2). Basis [p, sx]."""
@@ -382,7 +383,8 @@ def test_optimize_u_to_p_sx_p(self):
         passmanager.append(Optimize1qGatesDecomposition(basis))
         result = passmanager.run(circuit)
 
-        self.assertEqual(expected, result)
+        msg = f"expected:\n{expected}\nresult:\n{result}"
+        self.assertEqual(expected, result, msg=msg)
 
     def test_optimize_u3_to_u1(self):
         """U3(0, 0, pi/4) ->  U1(pi/4). Basis [u1, u2, u3]."""
@@ -399,7 +401,8 @@ def test_optimize_u3_to_u1(self):
         passmanager.append(Optimize1qGatesDecomposition(basis))
         result = passmanager.run(circuit)
 
-        self.assertEqual(expected, result)
+        msg = f"expected:\n{expected}\nresult:\n{result}"
+        self.assertEqual(expected, result, msg=msg)
 
     def test_optimize_u3_to_u2(self):
         """U3(pi/2, 0, pi/4) ->  U2(0, pi/4). Basis [u1, u2, u3]."""
@@ -416,7 +419,8 @@ def test_optimize_u3_to_u2(self):
         passmanager.append(Optimize1qGatesDecomposition(basis))
         result = passmanager.run(circuit)
 
-        self.assertEqual(expected, result)
+        msg = f"expected:\n{expected}\nresult:\n{result}"
+        self.assertEqual(expected, result, msg=msg)
 
 
 if __name__ == '__main__':