Unroll3qOrMore before layout allocation stage in the levels 0, 1, and…

… 2 (#7251) * level 0 * level 0 * level 1 and 2 * level 1 and 2 * always unroll * reduce diff * reno * _unroll3q without coupling map
Qiskit · Nov 30, 2021 · fe0abaa · fe0abaa
1 parent 4a94b77
commit fe0abaa
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Showing 5 changed files with 57 additions and 59 deletions.
diff --git a/qiskit/transpiler/preset_passmanagers/level0.py b/qiskit/transpiler/preset_passmanagers/level0.py
@@ -94,7 +94,20 @@ def level_0_pass_manager(pass_manager_config: PassManagerConfig) -> PassManager:
     unitary_synthesis_method = pass_manager_config.unitary_synthesis_method
     unitary_synthesis_plugin_config = pass_manager_config.unitary_synthesis_plugin_config
 
-    # 1. Choose an initial layout if not set by user (default: trivial layout)
+    # 1. Decompose so only 1-qubit and 2-qubit gates remain
+    _unroll3q = [
+        # Use unitary synthesis for basis aware decomposition of UnitaryGates
+        UnitarySynthesis(
+            basis_gates,
+            approximation_degree=approximation_degree,
+            method=unitary_synthesis_method,
+            min_qubits=3,
+            plugin_config=unitary_synthesis_plugin_config,
+        ),
+        Unroll3qOrMore(),
+    ]
+
+    # 2. Choose an initial layout if not set by user (default: trivial layout)
     _given_layout = SetLayout(initial_layout)
 
     def _choose_layout_condition(property_set):
@@ -111,24 +124,9 @@ def _choose_layout_condition(property_set):
     else:
         raise TranspilerError("Invalid layout method %s." % layout_method)
 
-    # 2. Extend dag/layout with ancillas using the full coupling map
+    # 3. Extend dag/layout with ancillas using the full coupling map
     _embed = [FullAncillaAllocation(coupling_map), EnlargeWithAncilla(), ApplyLayout()]
 
-    # 3. Decompose so only 1-qubit and 2-qubit gates remain
-    _unroll3q = [
-        # Use unitary synthesis for basis aware decomposition of UnitaryGates
-        UnitarySynthesis(
-            basis_gates,
-            approximation_degree=approximation_degree,
-            coupling_map=coupling_map,
-            backend_props=backend_properties,
-            method=unitary_synthesis_method,
-            min_qubits=3,
-            plugin_config=unitary_synthesis_plugin_config,
-        ),
-        Unroll3qOrMore(),
-    ]
-
     # 4. Swap to fit the coupling map
     _swap_check = CheckMap(coupling_map)
 
@@ -247,9 +245,9 @@ def _contains_delay(property_set):
     pm0 = PassManager()
     if coupling_map or initial_layout:
         pm0.append(_given_layout)
+        pm0.append(_unroll3q)
         pm0.append(_choose_layout, condition=_choose_layout_condition)
         pm0.append(_embed)
-        pm0.append(_unroll3q)
         pm0.append(_swap_check)
         pm0.append(_swap, condition=_swap_condition)
     pm0.append(_unroll)

diff --git a/qiskit/transpiler/preset_passmanagers/level1.py b/qiskit/transpiler/preset_passmanagers/level1.py
@@ -112,7 +112,20 @@ def level_1_pass_manager(pass_manager_config: PassManagerConfig) -> PassManager:
     def _choose_layout_condition(property_set):
         return not property_set["layout"]
 
-    # 2. Use a better layout on densely connected qubits, if circuit needs swaps
+    # 2. Decompose so only 1-qubit and 2-qubit gates remain
+    _unroll3q = [
+        # Use unitary synthesis for basis aware decomposition of UnitaryGates
+        UnitarySynthesis(
+            basis_gates,
+            approximation_degree=approximation_degree,
+            method=unitary_synthesis_method,
+            min_qubits=3,
+            plugin_config=unitary_synthesis_plugin_config,
+        ),
+        Unroll3qOrMore(),
+    ]
+
+    # 3. Use a better layout on densely connected qubits, if circuit needs swaps
     if layout_method == "trivial":
         _improve_layout = TrivialLayout(coupling_map)
     elif layout_method == "dense":
@@ -130,24 +143,9 @@ def _not_perfect_yet(property_set):
             and property_set["trivial_layout_score"] != 0
         )
 
-    # 3. Extend dag/layout with ancillas using the full coupling map
+    # 4. Extend dag/layout with ancillas using the full coupling map
     _embed = [FullAncillaAllocation(coupling_map), EnlargeWithAncilla(), ApplyLayout()]
 
-    # 4. Decompose so only 1-qubit and 2-qubit gates remain
-    _unroll3q = [
-        # Use unitary synthesis for basis aware decomposition of UnitaryGates
-        UnitarySynthesis(
-            basis_gates,
-            approximation_degree=approximation_degree,
-            coupling_map=coupling_map,
-            method=unitary_synthesis_method,
-            backend_props=backend_properties,
-            min_qubits=3,
-            plugin_config=unitary_synthesis_plugin_config,
-        ),
-        Unroll3qOrMore(),
-    ]
-
     # 5. Swap to fit the coupling map
     _swap_check = CheckMap(coupling_map)
 
@@ -279,10 +277,10 @@ def _contains_delay(property_set):
     pm1 = PassManager()
     if coupling_map or initial_layout:
         pm1.append(_given_layout)
+        pm1.append(_unroll3q)
         pm1.append(_choose_layout_and_score, condition=_choose_layout_condition)
         pm1.append(_improve_layout, condition=_not_perfect_yet)
         pm1.append(_embed)
-        pm1.append(_unroll3q)
         pm1.append(_swap_check)
         pm1.append(_swap, condition=_swap_condition)
     pm1.append(_unroll)

diff --git a/qiskit/transpiler/preset_passmanagers/level2.py b/qiskit/transpiler/preset_passmanagers/level2.py
@@ -105,7 +105,20 @@ def level_2_pass_manager(pass_manager_config: PassManagerConfig) -> PassManager:
     timing_constraints = pass_manager_config.timing_constraints or TimingConstraints()
     unitary_synthesis_plugin_config = pass_manager_config.unitary_synthesis_plugin_config
 
-    # 1. Search for a perfect layout, or choose a dense layout, if no layout given
+    # 1. Unroll to 1q or 2q gates
+    _unroll3q = [
+        # Use unitary synthesis for basis aware decomposition of UnitaryGates
+        UnitarySynthesis(
+            basis_gates,
+            approximation_degree=approximation_degree,
+            method=unitary_synthesis_method,
+            min_qubits=3,
+            plugin_config=unitary_synthesis_plugin_config,
+        ),
+        Unroll3qOrMore(),
+    ]
+
+    # 2. Search for a perfect layout, or choose a dense layout, if no layout given
     _given_layout = SetLayout(initial_layout)
 
     def _choose_layout_condition(property_set):
@@ -121,7 +134,7 @@ def _choose_layout_condition(property_set):
             Layout2qDistance(coupling_map, property_name="trivial_layout_score"),
         ]
     )
-    # 1b. If a trivial layout wasn't perfect (ie no swaps are needed) then try using
+    # 2b. If a trivial layout wasn't perfect (ie no swaps are needed) then try using
     # CSP layout to find a perfect layout
     _choose_layout_1 = (
         []
@@ -132,7 +145,7 @@ def _choose_layout_condition(property_set):
     def _trivial_not_perfect(property_set):
         # Verify that a trivial layout  is perfect. If trivial_layout_score > 0
         # the layout is not perfect. The layout is unconditionally set by trivial
-        # layout so we need to clear it before contuing.
+        # layout so we need to clear it before continuing.
         if property_set["trivial_layout_score"] is not None:
             if property_set["trivial_layout_score"] != 0:
                 return True
@@ -151,7 +164,7 @@ def _csp_not_found_match(property_set):
             return True
         return False
 
-    # 1c. if CSP layout doesn't converge on a solution use layout_method (dense) to get a layout
+    # 2c. if CSP layout doesn't converge on a solution use layout_method (dense) to get a layout
     if layout_method == "trivial":
         _choose_layout_2 = TrivialLayout(coupling_map)
     elif layout_method == "dense":
@@ -163,24 +176,9 @@ def _csp_not_found_match(property_set):
     else:
         raise TranspilerError("Invalid layout method %s." % layout_method)
 
-    # 2. Extend dag/layout with ancillas using the full coupling map
+    # 3. Extend dag/layout with ancillas using the full coupling map
     _embed = [FullAncillaAllocation(coupling_map), EnlargeWithAncilla(), ApplyLayout()]
 
-    # 3. Unroll to 1q or 2q gates
-    _unroll3q = [
-        # Use unitary synthesis for basis aware decomposition of UnitaryGates
-        UnitarySynthesis(
-            basis_gates,
-            approximation_degree=approximation_degree,
-            coupling_map=coupling_map,
-            backend_props=backend_properties,
-            method=unitary_synthesis_method,
-            min_qubits=3,
-            plugin_config=unitary_synthesis_plugin_config,
-        ),
-        Unroll3qOrMore(),
-    ]
-
     # 4. Swap to fit the coupling map
     _swap_check = CheckMap(coupling_map)
 
@@ -316,11 +314,11 @@ def _contains_delay(property_set):
     pm2 = PassManager()
     if coupling_map or initial_layout:
         pm2.append(_given_layout)
+        pm2.append(_unroll3q)
         pm2.append(_choose_layout_0, condition=_choose_layout_condition)
         pm2.append(_choose_layout_1, condition=_trivial_not_perfect)
         pm2.append(_choose_layout_2, condition=_csp_not_found_match)
         pm2.append(_embed)
-        pm2.append(_unroll3q)
         pm2.append(_swap_check)
         pm2.append(_swap, condition=_swap_condition)
     pm2.append(_unroll)

diff --git a/qiskit/transpiler/preset_passmanagers/level3.py b/qiskit/transpiler/preset_passmanagers/level3.py
@@ -114,8 +114,6 @@ def level_3_pass_manager(pass_manager_config: PassManagerConfig) -> PassManager:
         UnitarySynthesis(
             basis_gates,
             approximation_degree=approximation_degree,
-            coupling_map=coupling_map,
-            backend_props=backend_properties,
             method=unitary_synthesis_method,
             plugin_config=unitary_synthesis_plugin_config,
             min_qubits=3,

diff --git a/releasenotes/notes/7156-df1a60c608b93184.yaml b/releasenotes/notes/7156-df1a60c608b93184.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixed `#7156 <https://github.com/Qiskit/qiskit-terra/issues/7156>`__ .
+    Many layout methods ignore 3-or-more qubit gates resulting in expected layout allocation decisions.
+    The pass :class:`qiskit.transpiler.passes.Unroll3qOrMore` is now being executed before the layout pass.