mirror of https://github.com/Qiskit/qiskit.git
21 lines
1.0 KiB
YAML
21 lines
1.0 KiB
YAML
---
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issues:
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- |
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When running :func:`~qiskit.tools.parallel_map` (and functions that
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internally call :func:`~qiskit.tools.parallel_map` such as
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:func:`~qiskit.compiler.transpile` and :func:`~qiskit.compiler.assemble`)
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on Python 3.9 with ``QISKIT_PARALLEL`` set to True in some scenarios it is
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possible for the program to deadlock and never finish running. To avoid
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this from happening the default for Python 3.9 was changed to not run in
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parallel, but if ``QISKIT_PARALLEL`` is explicitly enabled then this
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can still occur.
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upgrade:
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The default value for ``QISKIT_PARALLEL`` on Python 3.9 environments has
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changed to ``False``, this means that when running on Python 3.9 by default
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multiprocessing will not be used. This was done to avoid a potential
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deadlock/hanging issue that can occur when running multiprocessing on
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Python 3.9 (see the known issues section for more detail). It is still
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possible to manual enable it by explicitly setting the ``QISKIT_PARALLEL``
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environment variable to ``TRUE``.
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