Merge branch 'main' into dag-fast-path

jakelishman · Sep 7, 2023 · 820649a · 820649a
2 parents 20a5407 + c5c6b11
commit 820649a
Show file tree

Hide file tree

Showing 3 changed files with 11 additions and 4 deletions.
diff --git a/crates/accelerate/src/sabre_swap/mod.rs b/crates/accelerate/src/sabre_swap/mod.rs
@@ -411,8 +411,8 @@ fn swap_map_trial(
                 qubits_decay.fill(1.);
                 num_search_steps = 0;
             } else {
-                qubits_decay[best_swap[0].index()] += DECAY_RATE;
-                qubits_decay[best_swap[1].index()] += DECAY_RATE;
+                qubits_decay[best_swap[0].to_phys(&layout).index()] += DECAY_RATE;
+                qubits_decay[best_swap[1].to_phys(&layout).index()] += DECAY_RATE;
             }
         }
         // If we exceeded the number of allowed attempts without successfully routing a node, we
@@ -713,7 +713,8 @@ fn choose_best_swap(
                     + EXTENDED_SET_WEIGHT * extended_set.score(swap, layout, dist)
             }
             Heuristic::Decay => {
-                qubits_decay[swap[0].index()].max(qubits_decay[swap[1].index()])
+                qubits_decay[swap[0].to_phys(layout).index()]
+                    .max(qubits_decay[swap[1].to_phys(layout).index()])
                     * (absolute_score
                         + layer.score(swap, layout, dist)
                         + EXTENDED_SET_WEIGHT * extended_set.score(swap, layout, dist))

diff --git a/releasenotes/notes/sabre-decay-physical-ad2f470cd45d69f3.yaml b/releasenotes/notes/sabre-decay-physical-ad2f470cd45d69f3.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    The ``"decay"`` heuristic of :class:`.SabreSwap` and :class:`.SabreLayout` now tracks the depth
+    correctly on physical qubits rather than mistakenly tracking the "depth" of swaps on virtual
+    qubits.
diff --git a/test/python/transpiler/test_sabre_layout.py b/test/python/transpiler/test_sabre_layout.py
@@ -60,7 +60,7 @@ def test_5q_circuit_20q_coupling(self):
         pass_.run(dag)
 
         layout = pass_.property_set["layout"]
-        self.assertEqual([layout[q] for q in circuit.qubits], [11, 10, 16, 5, 17])
+        self.assertEqual([layout[q] for q in circuit.qubits], [16, 7, 11, 12, 13])
 
     def test_6q_circuit_20q_coupling(self):
         """Test finds layout for 6q circuit on 20q device."""