PyTorch: The "freeze_support()" line can be omitted

Question:

Traceback (most recent call last):
File “”, line 1, in
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\spawn.py”, line 105, in spawn_main
exitcode = _main(fd)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\spawn.py”, line 114, in _main
prepare(preparation_data)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\spawn.py”, line 225, in prepare
_fixup_main_from_path(data[‘init_main_from_path’])
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\spawn.py”, line 277, in _fixup_main_from_path
run_name=“mp_main”)
File “D:\Anaconda\envs\gpu-env\lib\runpy.py”, line 263, in run_path
pkg_name=pkg_name, script_name=fname)
File “D:\Anaconda\envs\gpu-env\lib\runpy.py”, line 96, in _run_module_code
mod_name, mod_spec, pkg_name, script_name)
File “D:\Anaconda\envs\gpu-env\lib\runpy.py”, line 85, in _run_code
exec(code, run_globals)
File “G:\pycharm Project\PytorchLearning\first\Classifier.py”, line 135, in
main()
File “G:\pycharm Project\PytorchLearning\first\Classifier.py”, line 123, in main
dataiter = iter(trainloader)
File “D:\Anaconda\envs\gpu-env\lib\site-packages\torch\utils\data\dataloader.py”, line 278, in iter
return _MultiProcessingDataLoaderIter(self)
File “D:\Anaconda\envs\gpu-env\lib\site-packages\torch\utils\data\dataloader.py”, line 682, in init
w.start()
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\process.py”, line 112, in start
self._popen = self._Popen(self)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\context.py”, line 223, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\context.py”, line 322, in _Popen
return Popen(process_obj)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\popen_spawn_win32.py”, line 46, in init
prep_data = spawn.get_preparation_data(process_obj._name)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\spawn.py”, line 143, in get_preparation_data
_check_not_importing_main()
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\spawn.py”, line 136, 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 “G:/pycharm Project/PytorchLearning/first/Classifier.py”, line 135, in
main()
File “G:/pycharm Project/PytorchLearning/first/Classifier.py”, line 123, in main
dataiter = iter(trainloader)
File “D:\Anaconda\envs\gpu-env\lib\site-packages\torch\utils\data\dataloader.py”, line 278, in iter
return _MultiProcessingDataLoaderIter(self)
File “D:\Anaconda\envs\gpu-env\lib\site-packages\torch\utils\data\dataloader.py”, line 682, in init
w.start()
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\process.py”, line 112, in start
self._popen = self._Popen(self)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\context.py”, line 223, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\context.py”, line 322, in _Popen
return Popen(process_obj)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\popen_spawn_win32.py”, line 89, in init
reduction.dump(process_obj, to_child)
File “D:\Anaconda\envs\gpu-env\lib\multiprocessing\reduction.py”, line 60, in dump
ForkingPickler(file, protocol).dump(obj)
BrokenPipeError: [Errno 32] Broken pipe

Solution:

Add in the execution of the main program module:

if __name__ == '__main__':

problem solved!