问题
I'm trying to use the IBM Q Experience API and I installed the library and wrote a quick test code. At first, it couldn't find the module. Then, I added the whole sys thing. Admittedly, I just copied that from a stackoverflow post so that may be the problem. Anyways, I got "RunTime Error" which leads to the python multiprocessing lib. The IBM Q doesn't have a big community, so I couldn't find anything after researching a little while. I'm completely unfamiliar with multiprocessing, threading, etc, so I imagine just seeing the code and error will be better than anything I can do to explain. Thanks in advance.
import sys
sys.path.append("../../")
from qiskit import QuantumProgram
#visualization
from tools.visualization import plot_histogram
#set up registers
qp = QuantumProgram()
q = qp.create_quantum_register("q", 3)
c = qp.create_classical_register("c", 3)
#define our circuit
threeQ = qp.create_circuit("threeQ", [q], [c])
threeQ.measure(q[0], c[0])
threeQ.measure(q[1], c[1])
threeQ.measure(q[2], c[2])
#run
result = qp.execute(["threeQ"])
#plot
plot_histogram(result.get_counts("threeQ"))
The error I get (sorry, it's long):
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 106, in spawn_main
exitcode = _main(fd)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 115, in _main
prepare(preparation_data)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 226, in prepare
_fixup_main_from_path(data['init_main_from_path'])
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 278, in _fixup_main_from_path
run_name="__mp_main__")
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 254, in run_path
pkg_name=pkg_name, script_name=fname)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 96, in _run_module_code
mod_name, mod_spec, pkg_name, script_name)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:\Users\Everybody\firstquantum.py", line 21, in <module>
print(qp.execute(["threeQ"]))
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_quantumprogram.py", line 1413, in execute
result = self.run(qobj, wait=wait, timeout=timeout)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_quantumprogram.py", line 1232, in run
timeout=timeout)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_quantumprogram.py", line 1315, in _run_internal
job_processor.submit()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_jobprocessor.py", line 118, in submit
future = executor.submit(run_backend, q_job)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\concurrent\futures\process.py", line 454, in submit
self._start_queue_management_thread()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\concurrent\futures\process.py", line 415, in _start_queue_management_thread
self._adjust_process_count()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\concurrent\futures\process.py", line 434, in _adjust_process_count
p.start()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\process.py", line 105, in start
self._popen = self._Popen(self)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\context.py", line 212, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\context.py", line 313, in _Popen
return Popen(process_obj)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\popen_spawn_win32.py", line 34, in __init__
prep_data = spawn.get_preparation_data(process_obj._name)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 144, in get_preparation_data
_check_not_importing_main()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 137, in _check_not_importing_main
is not going to be frozen to produce an executable.''')
RuntimeError:
An attempt has been made to start a new process before the
current process has finished its bootstrapping phase.
This probably means that you are not using fork to start your
child processes and you have forgotten to use the proper idiom
in the main module:
if __name__ == '__main__':
freeze_support()
...
The "freeze_support()" line can be omitted if the program
is not going to be frozen to produce an executable.
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 106, in spawn_main
exitcode = _main(fd)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 115, in _main
prepare(preparation_data)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 226, in prepare
_fixup_main_from_path(data['init_main_from_path'])
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 278, in _fixup_main_from_path
run_name="__mp_main__")
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 254, in run_path
pkg_name=pkg_name, script_name=fname)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 96, in _run_module_code
mod_name, mod_spec, pkg_name, script_name)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:\Users\Everybody\firstquantum.py", line 21, in <module>
print(qp.execute(["threeQ"]))
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_quantumprogram.py", line 1413, in execute
result = self.run(qobj, wait=wait, timeout=timeout)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_quantumprogram.py", line 1232, in run
timeout=timeout)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_quantumprogram.py", line 1315, in _run_internal
job_processor.submit()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\site-packages\qiskit\_jobprocessor.py", line 118, in submit
future = executor.submit(run_backend, q_job)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\concurrent\futures\process.py", line 454, in submit
self._start_queue_management_thread()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\concurrent\futures\process.py", line 415, in _start_queue_management_thread
self._adjust_process_count()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\concurrent\futures\process.py", line 434, in _adjust_process_count
p.start()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\process.py", line 105, in start
self._popen = self._Popen(self)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\context.py", line 212, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\context.py", line 313, in _Popen
return Popen(process_obj)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\popen_spawn_win32.py", line 34, in __init__
prep_data = spawn.get_preparation_data(process_obj._name)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 144, in get_preparation_data
_check_not_importing_main()
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 137, in _check_not_importing_main
is not going to be frozen to produce an executable.''')
RuntimeError:
An attempt has been made to start a new process before the
current process has finished its bootstrapping phase.
This probably means that you are not using fork to start your
child processes and you have forgotten to use the proper idiom
in the main module:
if __name__ == '__main__':
freeze_support()
...
The "freeze_support()" line can be omitted if the program
is not going to be frozen to produce an executable.
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 106, in spawn_main
exitcode = _main(fd)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 115, in _main
prepare(preparation_data)
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 226, in prepare
_fixup_main_from_path(data['init_main_from_path'])
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\multiprocessing\spawn.py", line 278, in _fixup_main_from_path
run_name="__mp_main__")
File "C:\Users\Everybody\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 254, in run_path
ERROR
回答1:
This is a general issue with multi-threading in Python on Windows. The solution is to put your top-level code in an if __name__ == "__main__" block, as in:
if __name__ == '__main__':
<your code here>
Hope that helps!
来源：https://stackoverflow.com/questions/48453676/python-multiprocessing-error-with-ibm-api-q-experience