Recursion error while using QAOA from qiskit

[poojithurao]

Environment

• Covalent version: 0.106.0
• Python version: 3.8.13
• Operating system: Ubuntu 18.04.6 LTS
• Qiskit version: 0.36.2

What is happening?

I am using QAOA from the qiskit.algorithms package.

I created an electron function which just returns the QAOA object and called it inside a lattice function. I tried viewing the lattice through the .draw() function, but it is throwing RecursionError: maximum recursion depth exceeded error.

How can we reproduce the issue?

from qiskit.algorithms import QAOA
from qiskit.algorithms.optimizers import COBYLA
from qiskit import Aer

import covalent as ct

@ct.electron
def get_qaoa():
    return QAOA(COBYLA(), quantum_instance=Aer.get_backend('statevector_simulator'))

@ct.lattice
def qaoa_covalent():
    qaoa = get_qaoa()
    return None

qaoa_covalent.draw()

What should happen?

A proper Workflow graph was expected.

Any suggestions?

No response

[santoshkumarradha]

@cjao this is a wired bug, still getting this

from qiskit.algorithms import QAOA
from qiskit.algorithms.optimizers import COBYLA
from qiskit import Aer

import covalent as ct

@ct.electron
def get_qaoa():
    return QAOA(COBYLA(), quantum_instance=Aer.get_backend('statevector_simulator'))

@ct.lattice
def qaoa_covalent():
    qaoa = get_qaoa()
    return None

ct.dispatch(qaoa_covalent)()

Error Details

```python ---> 16 ct.dispatch(qaoa_covalent)() File [/opt/homebrew/Caskroom/miniconda/base/envs/qc/lib/python3.8/site-packages/covalent/_dispatcher_plugins/local.py:127](https://file+.vscode-resource.vscode-cdn.net/opt/homebrew/Caskroom/miniconda/base/envs/qc/lib/python3.8/site-packages/covalent/_dispatcher_plugins/local.py:127), in LocalDispatcher.dispatch..wrapper(*args, **kwargs) 123 nonlocal disable_run 125 lattice = deepcopy(orig_lattice) --> 127 lattice.build_graph(*args, **kwargs) 129 # Serialize the transport graph to JSON 130 json_lattice = lattice.serialize_to_json() File [/opt/homebrew/Caskroom/miniconda/base/envs/qc/lib/python3.8/site-packages/covalent/_workflow/lattice.py:216](https://file+.vscode-resource.vscode-cdn.net/opt/homebrew/Caskroom/miniconda/base/envs/qc/lib/python3.8/site-packages/covalent/_workflow/lattice.py:216), in Lattice.build_graph(self, *args, **kwargs) 212 self.kwargs = {k: TransportableObject.make_transportable(v) for k, v in kwargs.items()} 214 self.transport_graph.reset() --> 216 workflow_function = self.workflow_function.get_deserialized() 218 named_args, named_kwargs = get_named_params(workflow_function, self.args, self.kwargs) 219 self.named_args = named_args File [/opt/homebrew/Caskroom/miniconda/base/envs/qc/lib/python3.8/site-packages/covalent/_workflow/transportable_object.py:255](https://file+.vscode-resource.vscode-cdn.net/opt/homebrew/Caskroom/miniconda/base/envs/qc/lib/python3.8/site-packages/covalent/_workflow/transportable_object.py:255), in TransportableObject.get_deserialized(self) 245 def get_deserialized(self) -> Callable: 246 """ 247 Get the deserialized transportable object. ... --> 130 if not self.aer: 131 try: 132 from qiskit.providers import aer ```

---

Cloud pickling seems to work

import cloudpickle as pickle
a=pickle.dumps(QAOA(COBYLA(), quantum_instance=Aer.get_backend('statevector_simulator')))
pickle.loads(a)

So not sure where the recursion is happening.

[cjao]

@santoshkumarradha Feel free to assign this to me, but I probably won't be able to dig into it until mid next week at the earliest.

[Zasha01]

@santoshkumarradha How exactly did you fix it? I would appreciate your help.

It is still not working with the following code:

from qiskit.algorithms import QAOA
from qiskit.algorithms.optimizers import COBYLA
from qiskit import Aer

import covalent as ct
import cloudpickle

@ct.electron
def get_qaoa():
    qaoa = QAOA(COBYLA(), quantum_instance=Aer.get_backend('statevector_simulator'))
    return cloudpickle.dumps(qaoa)

@ct.lattice
def qaoa_covalent():
    qaoa_serialized = get_qaoa()
    qaoa = cloudpickle.loads(qaoa_serialized)
    return None

ct.dispatch(qaoa_covalent)()