Honor initial_layout when coupling map is None

qiskit/transpiler/passes/layout/full_ancilla_allocation.py

@@ -65,10 +65,17 @@ def run(self, dag):
         if layout is None:
             raise TranspilerError('FullAncillaAllocation pass requires property_set["layout"].')
 
-        layout_physical_qubits = layout.get_physical_bits().keys()
-        coupling_physical_qubits = self.coupling_map.physical_qubits
-        idle_physical_qubits = [q for q in coupling_physical_qubits
-                                if q not in layout_physical_qubits]
+        if layout:
+            layout_physical_qubits = list(range(max(layout.get_physical_bits()) + 1))
+        else:
+            layout_physical_qubits = []
+
+        idle_physical_qubits = [q for q in layout_physical_qubits
+                                if q not in layout.get_physical_bits()]
+
+        if self.coupling_map:
+            idle_physical_qubits = [q for q in self.coupling_map.physical_qubits
+                                    if q not in layout.get_physical_bits()]
 
         if idle_physical_qubits:
             if self.ancilla_name in dag.qregs:

qiskit/transpiler/passes/utils/check_map.py

@@ -43,6 +43,9 @@ def run(self, dag):
         """
         self.property_set['is_swap_mapped'] = True
 
+        if self.coupling_map is None:
+            return
+
         for gate in dag.two_qubit_ops():
             physical_q0 = gate.qargs[0].index
             physical_q1 = gate.qargs[1].index

qiskit/transpiler/preset_passmanagers/level0.py

@@ -160,7 +160,7 @@ def _direction_condition(property_set):
 
     # Build pass manager
     pm0 = PassManager()
-    if coupling_map:
+    if coupling_map or initial_layout:
         pm0.append(_given_layout)
         pm0.append(_choose_layout, condition=_choose_layout_condition)
         pm0.append(_embed)

qiskit/transpiler/preset_passmanagers/level1.py

@@ -193,7 +193,7 @@ def _opt_control(property_set):
 
     # Build pass manager
     pm1 = PassManager()
-    if coupling_map:
+    if coupling_map or initial_layout:
         pm1.append(_given_layout)
         pm1.append(_choose_layout_and_score, condition=_choose_layout_condition)
         pm1.append(_improve_layout, condition=_not_perfect_yet)

qiskit/transpiler/preset_passmanagers/level2.py

@@ -188,7 +188,7 @@ def _opt_control(property_set):
 
     # Build pass manager
     pm2 = PassManager()
-    if coupling_map:
+    if coupling_map or initial_layout:
         pm2.append(_given_layout)
         pm2.append(_choose_layout_1, condition=_choose_layout_condition)
         pm2.append(_choose_layout_2, condition=_choose_layout_condition)

qiskit/transpiler/preset_passmanagers/level3.py

@@ -207,7 +207,7 @@ def _opt_control(property_set):
     pm3 = PassManager()
     pm3.append(_unroll3q)
     pm3.append(_reset + _meas)
-    if coupling_map:
+    if coupling_map or initial_layout:
         pm3.append(_given_layout)
         pm3.append(_choose_layout_1, condition=_choose_layout_condition)
         pm3.append(_choose_layout_2, condition=_choose_layout_condition)

test/python/transpiler/test_preset_passmanagers.py

@@ -167,6 +167,40 @@ def test_symmetric_coupling_map(self, level):
         self.assertIn('ApplyLayout', self.passes)
         self.assertNotIn('CheckCXDirection', self.passes)
 
+    @data(0, 1, 2, 3)
+    def test_inital_layout_fully_connected_cm(self, level):
+        """Honor initial_layout when coupling_map=None
+        See: https://github.com/Qiskit/qiskit-terra/issues/5345
+        """
+        qr = QuantumRegister(2, 'q')
+        qc = QuantumCircuit(qr)
+        qc.h(qr[0])
+        qc.cx(qr[0], qr[1])
+
+        transpiled = transpile(qc, initial_layout=[0, 1], optimization_level=level,
+                               callback=self.callback)
+
+        self.assertIn('SetLayout', self.passes)
+        self.assertIn('ApplyLayout', self.passes)
+        self.assertEqual(len(transpiled._layout), 2)
+
+    @data(0, 1, 2, 3)
+    def test_partial_layout_fully_connected_cm(self, level):
+        """Honor initial_layout (partially defined) when coupling_map=None
+        See: https://github.com/Qiskit/qiskit-terra/issues/5345
+        """
+        qr = QuantumRegister(2, 'q')
+        qc = QuantumCircuit(qr)
+        qc.h(qr[0])
+        qc.cx(qr[0], qr[1])
+
+        transpiled = transpile(qc, initial_layout=[4, 2], optimization_level=level,
+                               callback=self.callback)
+
+        self.assertIn('SetLayout', self.passes)
+        self.assertIn('ApplyLayout', self.passes)
+        self.assertEqual(len(transpiled._layout), 5)
+
 
 @ddt
 class TestInitialLayouts(QiskitTestCase):