DAGCircuit with vars does not compare equal after pickling #14007
Description
Environment
- Qiskit version:
a00279bc7d6005bfc5ea783cd1fe336784160518 - Python version: 3.11
- Operating system: macOS Sonoma 14.4
What is happening?
After pickling, DAGCircuit is no longer equal to itself if it contains variables.
This issue predates all changes made in support of stretch (the above test fails on the commit prior to the first PR in that series).
How can we reproduce the issue?
def test_pickle_identifiers(self):
"""Test identifiers preserved through pickle."""
a = expr.Var.new("a", types.Bool())
b = expr.Var.new("b", types.Uint(8))
# Check captures and declarations.
dag = DAGCircuit()
dag.add_declared_var(a)
dag.add_captured_var(b)
self.assertEqual(dag.num_vars, 2)
self.assertEqual(dag.num_captured_vars, 1)
self.assertEqual(dag.num_declared_vars, 1)
with io.BytesIO() as buf:
pickle.dump(dag, buf)
buf.seek(0)
output = pickle.load(buf)
self.assertEqual(output.num_vars, 2)
self.assertEqual(output.num_captured_vars, 1)
self.assertEqual(output.num_declared_vars, 1)
self.assertEqual(output, dag) # < --- FAILSWhat should happen?
The circuits should be equal.
Any suggestions?
No response