Two problems:
- The Python extension is compiled without OpenMP support even though TH is built with it, so set_num_threads is incorrectly a no-op / warning
- Python is complaining about the return value
>>> torch.set_num_threads(1)
__main__:1: RuntimeWarning: set_num_threads is a no-op - torch was compiled without OpenMP support
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
SystemError: <built-in function set_num_threads> returned NULL without setting an error
Two problems: