mirror of
https://github.com/PiBrewing/craftbeerpi4.git
synced 2024-12-29 17:01:44 +01:00
107 lines
3.3 KiB
Python
107 lines
3.3 KiB
Python
"""Convenient parallelization of higher order functions.
|
|
|
|
This module provides two helper functions, with appropriate fallbacks on
|
|
Python 2 and on systems lacking support for synchronization mechanisms:
|
|
|
|
- map_multiprocess
|
|
- map_multithread
|
|
|
|
These helpers work like Python 3's map, with two differences:
|
|
|
|
- They don't guarantee the order of processing of
|
|
the elements of the iterable.
|
|
- The underlying process/thread pools chop the iterable into
|
|
a number of chunks, so that for very long iterables using
|
|
a large value for chunksize can make the job complete much faster
|
|
than using the default value of 1.
|
|
"""
|
|
|
|
__all__ = ['map_multiprocess', 'map_multithread']
|
|
|
|
from contextlib import contextmanager
|
|
from multiprocessing import Pool as ProcessPool
|
|
from multiprocessing.dummy import Pool as ThreadPool
|
|
|
|
from pip._vendor.requests.adapters import DEFAULT_POOLSIZE
|
|
from pip._vendor.six import PY2
|
|
from pip._vendor.six.moves import map
|
|
|
|
from pip._internal.utils.typing import MYPY_CHECK_RUNNING
|
|
|
|
if MYPY_CHECK_RUNNING:
|
|
from multiprocessing import pool
|
|
from typing import Callable, Iterable, Iterator, TypeVar, Union
|
|
|
|
Pool = Union[pool.Pool, pool.ThreadPool]
|
|
S = TypeVar('S')
|
|
T = TypeVar('T')
|
|
|
|
# On platforms without sem_open, multiprocessing[.dummy] Pool
|
|
# cannot be created.
|
|
try:
|
|
import multiprocessing.synchronize # noqa
|
|
except ImportError:
|
|
LACK_SEM_OPEN = True
|
|
else:
|
|
LACK_SEM_OPEN = False
|
|
|
|
# Incredibly large timeout to work around bpo-8296 on Python 2.
|
|
TIMEOUT = 2000000
|
|
|
|
|
|
@contextmanager
|
|
def closing(pool):
|
|
# type: (Pool) -> Iterator[Pool]
|
|
"""Return a context manager making sure the pool closes properly."""
|
|
try:
|
|
yield pool
|
|
finally:
|
|
# For Pool.imap*, close and join are needed
|
|
# for the returned iterator to begin yielding.
|
|
pool.close()
|
|
pool.join()
|
|
pool.terminate()
|
|
|
|
|
|
def _map_fallback(func, iterable, chunksize=1):
|
|
# type: (Callable[[S], T], Iterable[S], int) -> Iterator[T]
|
|
"""Make an iterator applying func to each element in iterable.
|
|
|
|
This function is the sequential fallback either on Python 2
|
|
where Pool.imap* doesn't react to KeyboardInterrupt
|
|
or when sem_open is unavailable.
|
|
"""
|
|
return map(func, iterable)
|
|
|
|
|
|
def _map_multiprocess(func, iterable, chunksize=1):
|
|
# type: (Callable[[S], T], Iterable[S], int) -> Iterator[T]
|
|
"""Chop iterable into chunks and submit them to a process pool.
|
|
|
|
For very long iterables using a large value for chunksize can make
|
|
the job complete much faster than using the default value of 1.
|
|
|
|
Return an unordered iterator of the results.
|
|
"""
|
|
with closing(ProcessPool()) as pool:
|
|
return pool.imap_unordered(func, iterable, chunksize)
|
|
|
|
|
|
def _map_multithread(func, iterable, chunksize=1):
|
|
# type: (Callable[[S], T], Iterable[S], int) -> Iterator[T]
|
|
"""Chop iterable into chunks and submit them to a thread pool.
|
|
|
|
For very long iterables using a large value for chunksize can make
|
|
the job complete much faster than using the default value of 1.
|
|
|
|
Return an unordered iterator of the results.
|
|
"""
|
|
with closing(ThreadPool(DEFAULT_POOLSIZE)) as pool:
|
|
return pool.imap_unordered(func, iterable, chunksize)
|
|
|
|
|
|
if LACK_SEM_OPEN or PY2:
|
|
map_multiprocess = map_multithread = _map_fallback
|
|
else:
|
|
map_multiprocess = _map_multiprocess
|
|
map_multithread = _map_multithread
|