QSVM fails under Python 3.8.5

[woodsp-ibm]

Hello, I am trying this modification using the simple updated tutorial: https://github.com/Qiskit/qiskit-tutorials/blob/master/legacy_tutorials/aqua/machine_learning/qsvm_classification.ipynb

I notice that everything works fine using Python 3.7.7 BUT using the newest python 3.8.5 only the jupyter version of this code is working. If I run it as a code, the qsvm.run instance create n subprocesses of the same instances going into a endless loop...the code recall itself....

The above was a comment in PR #1190 from @grossiM The other PR is related to QSVM but different so I broke this out here.

@grossiM Can I ask for some other information that can be of help to us. Such as what version are you running when you see this and what platform are you using

[grossiM]

Hello Steve, thanks for splitting up this problem. I attach my python code and the output file that I am running on a MacBook Pro (15-inch, 2019): 2,3 GHz 8-Core Intel Core i9 ProductName: Mac OS X ProductVersion: 10.15.5 BuildVersion: 19F101 executed into Anaconda(conda 4.8.3) env generated with: Python 3.8.5 and the latest qiskit ('qiskit-terra': '0.15.1', 'qiskit-aer': '0.6.1', 'qiskit-ignis': '0.4.0', 'qiskit-ibmq-provider': '0.8.0', 'qiskit-aqua': '0.7.5', 'qiskit': '0.20.0') with the modification described https://github.com/Qiskit/qiskit-aqua/pull/1190/commits/51789a6657c20e4c8ea5747870f4fa262fc44694

output.log THE CODE IS HERE:

`import matplotlib.pyplot as plt import numpy as np from qiskit import BasicAer from qiskit.ml.datasets import * from qiskit.circuit.library import ZZFeatureMap from qiskit.aqua.utils import split_dataset_to_data_and_labels, map_label_to_class_name from qiskit.aqua import QuantumInstance from qiskit.aqua.algorithms import QSVM import qiskit print(qiskit.__qiskit_version__) import logging from qiskit.aqua import set_qiskit_aqua_logging set_qiskit_aqua_logging(logging.DEBUG)

feature_dim=2 # we support feature_dim 2 or 3 sample_Total, training_input, test_input, class_labels = ad_hoc_data( training_size=20, test_size=10, n=feature_dim, gap=0.3, plot_data=False ) extra_test_data = sample_ad_hoc_data(sample_Total, 10, n=feature_dim) datapoints, class_to_label = split_dataset_to_data_and_labels(extra_test_data)

seed = 10598 feature_map = ZZFeatureMap(feature_dimension=feature_dim, reps=2, entanglement='linear') qsvm = QSVM(feature_map, training_input, test_input, datapoints[0])

backend = BasicAer.get_backend('qasm_simulator') quantum_instance = QuantumInstance(backend, shots=1024, seed_simulator=seed, seed_transpiler=seed) print('A'10) result = qsvm.run(quantum_instance) print('B'10)

[manoelmarques]

Everybody should always include if __name__ == "__main__": in their python scripts.

[manoelmarques]

This version works fine:

""" test """

import matplotlib.pyplot as plt
import numpy as np
from qiskit import BasicAer
from qiskit.ml.datasets import *
from qiskit.circuit.library import ZZFeatureMap
from qiskit.aqua.utils import split_dataset_to_data_and_labels, map_label_to_class_name
from qiskit.aqua import QuantumInstance
from qiskit.aqua.algorithms import QSVM
import qiskit
import logging
from qiskit.aqua import set_qiskit_aqua_logging

if __name__ == "__main__":
    # print(qiskit.qiskit_version)
    # set_qiskit_aqua_logging(logging.DEBUG)
    feature_dim = 2  # we support feature_dim 2 or 3
    sample_Total, training_input, test_input, class_labels = ad_hoc_data(training_size=20,
                                                                         test_size=10,
                                                                         n=feature_dim,
                                                                         gap=0.3,
                                                                         plot_data=False)
    extra_test_data = sample_ad_hoc_data(sample_Total, 10, n=feature_dim)
    datapoints, class_to_label = split_dataset_to_data_and_labels(extra_test_data)

    seed = 10598
    feature_map = ZZFeatureMap(feature_dimension=feature_dim, reps=2, entanglement='linear')
    qsvm = QSVM(feature_map, training_input, test_input, datapoints[0])

    backend = BasicAer.get_backend('qasm_simulator')
    quantum_instance = QuantumInstance(backend, shots=1024, seed_simulator=seed, seed_transpiler=seed)
    print('A'*10)
    result = qsvm.run(quantum_instance)
    print('B'*10)

[manoelmarques]

If one runs everything at global level, the multiprocessing module may spawn new processes that will import your whole module (file) hence the strange multiple print outputs. Adding __name__ == "__main__": should be added to any python script to avoid those side effects.

[grossiM]

Hello, thank you very much for the input. Yes, it's working fine now. In previous release I was working without the if name == "main": and it was working, from now on I will include it.

[woodsp-ibm]

As your issue is solved I will close this. I will note that multiprocessing changed in python in 3.8 from what it was in 3.7 hence that is explanation around the behavior change.