[WIP] Fix memory usage issues in BasisTranslator, BarrierBeforeFinalMeasurements, DAGFixedPoint and Decompose transpiler passes, fixes issue #7485

qiskit/transpiler/passes/basis/decompose.py

@@ -44,6 +44,7 @@ def __init__(
             self.gates_to_decompose = gate
         else:
             self.gates_to_decompose = gates_to_decompose
+        self._make_gate_lists()
 
     @property
     def gate(self) -> Gate:
@@ -74,6 +75,19 @@ def gate(self, value):
             stacklevel=2,
         )
         self.gates_to_decompose = value
+        self._make_gate_lists()
+
+    def _make_gate_lists(self):
+        """Make comparison lists for the gate list"""
+        if not isinstance(self.gates_to_decompose, list):
+            gates = [self.gates_to_decompose]
+        else:
+            gates = self.gates_to_decompose
+
+        self._strings_list, self._gate_type_list = [], []
+        if gates is not None:
+            self._strings_list = [s for s in gates if isinstance(s, str)]
+            self._gate_type_list = [g for g in gates if isinstance(g, type)]
 
     def run(self, dag: DAGCircuit) -> DAGCircuit:
         """Run the Decompose pass on `dag`.
@@ -114,22 +128,19 @@ def _should_decompose(self, node) -> bool:
         else:
             gates = self.gates_to_decompose
 
-        strings_list = [s for s in gates if isinstance(s, str)]
-        gate_type_list = [g for g in gates if isinstance(g, type)]
-
         if hasattr(node.op, "label") and node.op.label is not None:
             has_label = True
 
         if has_label and (  # check if label or label wildcard is given
-            node.op.label in gates or any(fnmatch(node.op.label, p) for p in strings_list)
+            node.op.label in gates or any(fnmatch(node.op.label, p) for p in self._strings_list)
         ):
             return True
         elif not has_label and (  # check if name or name wildcard is given
-            node.name in gates or any(fnmatch(node.name, p) for p in strings_list)
+            node.name in gates or any(fnmatch(node.name, p) for p in self._strings_list)
         ):
             return True
         elif not has_label and (  # check if Gate type given
-            any(isinstance(node.op, op) for op in gate_type_list)
+            any(isinstance(node.op, op) for op in self._gate_type_list)
         ):
             return True
         else:

qiskit/transpiler/passes/utils/dag_fixed_point.py

@@ -32,5 +32,5 @@ def run(self, dag):
         else:
             fixed_point_reached = self.property_set["_dag_fixed_point_previous_dag"] == dag
             self.property_set["dag_fixed_point"] = fixed_point_reached
-
+            del self.property_set["_dag_fixed_point_previous_dag"]
         self.property_set["_dag_fixed_point_previous_dag"] = deepcopy(dag)

qiskit/transpiler/passes/utils/merge_adjacent_barriers.py

@@ -101,7 +101,7 @@ def _collect_potential_merges(dag, barriers):
         # Start from the first barrier
         current_barrier = barriers[0]
         end_of_barrier = current_barrier
-        current_barrier_nodes = [current_barrier]
+        current_barrier_nodes = set([current_barrier])
 
         current_qubits = set(current_barrier.qargs)
         current_ancestors = dag.ancestors(current_barrier)
@@ -140,7 +140,7 @@ def _collect_potential_merges(dag, barriers):
                     barrier_to_add = Barrier(len(current_qubits))
 
                     end_of_barrier = next_barrier
-                    current_barrier_nodes.append(end_of_barrier)
+                    current_barrier_nodes.add(end_of_barrier)
 
                     continue
 
@@ -156,10 +156,10 @@ def _collect_potential_merges(dag, barriers):
             current_descendants = dag.descendants(next_barrier)
 
             barrier_to_add = Barrier(len(current_qubits))
-            current_barrier_nodes = []
+            current_barrier_nodes = set()
 
             end_of_barrier = next_barrier
-            current_barrier_nodes.append(end_of_barrier)
+            current_barrier_nodes.add(end_of_barrier)
 
         if barrier_to_add:
             node_to_barrier_qubits[end_of_barrier] = current_qubits