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Fix Python 3.12 deprecation warning about os.fork() #1070

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Merged
mhucka merged 2 commits into from
Jun 5, 2025
Merged

Fix Python 3.12 deprecation warning about os.fork() #1070

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4b8c9b5
I addressed the multiprocessing warnings in the performance benchmarks.
google-labs-jules[bot] Jun 4, 2025
8537a7b
Merge branch 'master' into fix-multiprocessing-warnings
mhucka Jun 4, 2025
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6 changes: 6 additions & 0 deletions src/openfermion/linalg/linear_qubit_operator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -144,6 +144,8 @@ def _matvec(self, x):
class ParallelLinearQubitOperator(scipy.sparse.linalg.LinearOperator):
"""A LinearOperator from a QubitOperator with multiple processors."""

_start_method_set = False

def __init__(self, qubit_operator, n_qubits=None, options=None):
"""
Args:
Expand All @@ -162,6 +164,10 @@ def __init__(self, qubit_operator, n_qubits=None, options=None):
self.n_qubits = n_qubits
self.options = options or LinearQubitOperatorOptions()

if not ParallelLinearQubitOperator._start_method_set:
multiprocessing.set_start_method('forkserver', force=True)
ParallelLinearQubitOperator._start_method_set = True

self.qubit_operator_groups = list(
qubit_operator.get_operator_groups(self.options.processes)
)
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