- 1 year ago
Using multiprocessing on macOS vs. Windows
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When using the multiprocessing
module in Python, there are some differences between macOS and Windows due to the underlying operating system and the way processes are managed. Here are some important considerations when using multiprocessing
on macOS and Windows:
Process Creation:
- On macOS,
multiprocessing
uses thefork
method to create child processes. Thefork
method creates a new process that is a copy of the parent process, including all its memory and resources. This makes process creation relatively fast. - On Windows,
multiprocessing
uses thespawn
method to create child processes. Thespawn
method creates a new process by starting a new Python interpreter, importing the calling script, and running it. This means that the child process starts with a fresh interpreter and does not inherit any state from the parent process. Process creation usingspawn
can be slower thanfork
.
- On macOS,
Sharing Data:
- On macOS, the
multiprocessing
module supports sharing data between processes using shared memory with theValue
andArray
objects, as well as usingManager
objects for more complex data structures. Thefork
method allows data to be shared easily between parent and child processes. - On Windows, the
multiprocessing
module supports sharing data using theManager
objects. However, shared memory withValue
andArray
objects is not available, and you may need to use other inter-process communication (IPC) mechanisms like pipes or sockets to share data between processes.
- On macOS, the
Signals:
- On macOS, the
multiprocessing
module supports using signals to communicate between processes. - On Windows, the
multiprocessing
module does not support signals due to the differences in the underlying process management.
- On macOS, the
Fork Safety:
- When using the
fork
method on macOS, it is essential to ensure that your code is "fork-safe." Fork safety means that the code can be safely executed in a forked child process without causing issues. This is because the child process inherits the state of the parent process, including all open file handles, network connections, and other resources. Not all libraries or code may be fork-safe.
- When using the
In general, multiprocessing
on macOS tends to be more similar to using threads, while on Windows, it behaves more like separate processes due to the lack of fork
support. When writing code that uses multiprocessing
, it's essential to be aware of these differences and design your code accordingly to ensure it works correctly on both platforms.