当通过cypari2使用Pari时，我在尝试并行运行几个循环时遇到了麻烦。我将在Tracebacks中包括几个小的工作示例，以防有人对此有所了解。
示例1——using joblib:
from cypari2 import Pari
from joblib import Parallel, delayed
def AddOne(v):
return v + pari.one()
pari = Pari()
vec = [pari('x_1'), pari('x_2')]
print(vec)
#works
newVec = Parallel(n_jobs=1)(delayed(AddOne)(i) for i in vec)
print(newVec)
#doesn't work
newVec2 = Parallel(n_jobs=2)(delayed(AddOne)(i) for i in vec)
print(newVec2)
输出:
[x_1, x_2]
[x_1 + 1, x_2 + 1]
joblib.externals.loky.process_executor._RemoteTraceback:
"""
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/joblib/externals/loky/backend/queues.py", line 150, in _feed
obj_ = dumps(obj, reducers=reducers)
File "/usr/lib/python3/dist-packages/joblib/externals/loky/backend/reduction.py", line 247, in dumps
dump(obj, buf, reducers=reducers, protocol=protocol)
File "/usr/lib/python3/dist-packages/joblib/externals/loky/backend/reduction.py", line 240, in dump
_LokyPickler(file, reducers=reducers, protocol=protocol).dump(obj)
File "/usr/lib/python3/dist-packages/joblib/externals/cloudpickle/cloudpickle_fast.py", line 538, in dump
return Pickler.dump(self, obj)
File "stringsource", line 2, in cypari2.pari_instance.Pari.__reduce_cython__
TypeError: no default __reduce__ due to non-trivial __cinit__
"""
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "min_jake_joblib.py", line 16, in <module>
newVec2 = Parallel(n_jobs=2)(delayed(AddOne)(i) for i in vec)
File "/usr/lib/python3/dist-packages/joblib/parallel.py", line 1016, in __call__
self.retrieve()
File "/usr/lib/python3/dist-packages/joblib/parallel.py", line 908, in retrieve
self._output.extend(job.get(timeout=self.timeout))
File "/usr/lib/python3/dist-packages/joblib/_parallel_backends.py", line 554, in wrap_future_result
return future.result(timeout=timeout)
File "/usr/lib/python3.8/concurrent/futures/_base.py", line 444, in result
return self.__get_result()
File "/usr/lib/python3.8/concurrent/futures/_base.py", line 389, in __get_result
raise self._exception
_pickle.PicklingError: Could not pickle the task to send it to the workers.
似乎是一个问题与酸洗Pari对象，但有什么办法解决它?
示例2——使用multiprocessing:
from cypari2 import Pari
import multiprocessing
def AddOne(v):
return v + pari.one()
pari = Pari()
vec = [pari('x_1'), pari('x_2')]
print(vec)
#doesn't work
if __name__ == '__main__':
pool = multiprocessing.Pool(processes = 2) ## doesn't matter how many I use
newVec = pool.map(AddOne, (i for i in vec))
print(newVec)
它会隔离错误，但不会完全自动退出，所以我必须使用Ctrl^C来终止它。输出:
[x_1, x_2]
Exception in thread Thread-3:
Traceback (most recent call last):
File "/usr/lib/python3.8/threading.py", line 932, in _bootstrap_inner
self.run()
File "/usr/lib/python3.8/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib/python3.8/multiprocessing/pool.py", line 576, in _handle_results
task = get()
File "/usr/lib/python3.8/multiprocessing/connection.py", line 251, in recv
return _ForkingPickler.loads(buf.getbuffer())
File "cypari2/gen.pyx", line 4705, in cypari2.gen.objtogen
File "cypari2/gen.pyx", line 4812, in cypari2.gen.objtogen
File "cypari2/convert.pyx", line 557, in cypari2.convert.PyObject_AsGEN
cysignals.signals.SignalError: Segmentation fault
^CProcess ForkPoolWorker-1:
Process ForkPoolWorker-2:
Traceback (most recent call last):
File "min_jake_multiprocessing.py", line 14, in <module>
Traceback (most recent call last):
File "/usr/lib/python3.8/multiprocessing/process.py", line 315, in _bootstrap
self.run()
File "/usr/lib/python3.8/multiprocessing/process.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib/python3.8/multiprocessing/pool.py", line 114, in worker
task = get()
Traceback (most recent call last):
File "/usr/lib/python3.8/multiprocessing/queues.py", line 356, in get
res = self._reader.recv_bytes()
File "/usr/lib/python3.8/multiprocessing/connection.py", line 216, in recv_bytes
buf = self._recv_bytes(maxlength)
File "/usr/lib/python3.8/multiprocessing/connection.py", line 414, in _recv_bytes
buf = self._recv(4)
File "/usr/lib/python3.8/multiprocessing/connection.py", line 379, in _recv
chunk = read(handle, remaining)
File "src/cysignals/signals.pyx", line 320, in cysignals.signals.python_check_interrupt
File "/usr/lib/python3.8/multiprocessing/process.py", line 315, in _bootstrap
self.run()
File "/usr/lib/python3.8/multiprocessing/process.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib/python3.8/multiprocessing/pool.py", line 114, in worker
task = get()
File "/usr/lib/python3.8/multiprocessing/queues.py", line 355, in get
with self._rlock:
File "/usr/lib/python3.8/multiprocessing/synchronize.py", line 95, in __enter__
return self._semlock.__enter__()
File "src/cysignals/signals.pyx", line 320, in cysignals.signals.python_check_interrupt
KeyboardInterrupt
KeyboardInterrupt
newVec = pool.map(AddOne, (i for i in vec))
File "/usr/lib/python3.8/multiprocessing/pool.py", line 364, in map
return self._map_async(func, iterable, mapstar, chunksize).get()
File "/usr/lib/python3.8/multiprocessing/pool.py", line 765, in get
self.wait(timeout)
File "/usr/lib/python3.8/multiprocessing/pool.py", line 762, in wait
self._event.wait(timeout)
File "/usr/lib/python3.8/threading.py", line 558, in wait
signaled = self._cond.wait(timeout)
File "/usr/lib/python3.8/threading.py", line 302, in wait
waiter.acquire()
File "src/cysignals/signals.pyx", line 320, in cysignals.signals.python_check_interrupt
KeyboardInterrupt
Traceback (most recent call last):
File "/usr/lib/python3.8/multiprocessing/util.py", line 300, in _run_finalizers
finalizer()
File "/usr/lib/python3.8/multiprocessing/util.py", line 224, in __call__
res = self._callback(*self._args, **self._kwargs)
File "/usr/lib/python3.8/multiprocessing/pool.py", line 695, in _terminate_pool
raise AssertionError(
AssertionError: Cannot have cache with result_hander not alive
我想有人会告诉我使用sympy或其他符号代数包代替，但是我需要做的符号代数相当复杂，Pari可以处理得非常好。但是，最终我希望能够并行地处理包含Pari对象的类对象队列。如有任何意见或建议，欢迎。
好吧，这不是一个完整的答案，但它适用于我，所以我想分享一下，以防其他人遇到这个问题。
第一个问题似乎是apt存储库上的libpari-dev和pari-gp的版本太旧了。apt存储库包含2.11版本，而Pari的git存储库中的版本是2.14版本。卸载并按照这里的说明从源代码安装解决了我的大部分问题。
有趣的是，我仍然需要从apt存储库安装libpari-gmp-tls6才能使其正常工作。但是，在那之后，我能够让上面的测试示例运行。使用多处理的示例无需修改即可成功运行，但使用joblib的示例需要使用"threading"后端: