IssueRaiser

>> The GIL is definitely no source of unicorns and rainbows, but I think the case against it is usually overstated.

>> The GIL is definitely no source of unicorns and rainbows, but I think the case against it is usually overstated. There are numerous ways of sidestepping it (multiprocessing, pypy, C extensions, etc.), and it does serve a useful purpose. That's definitely all true, but the article brushes it's implications for multithreaded Python off as if they don't exist, which is what one of the posters above me was probably referring to. Yes you can do multiprocessing, but if I have lots of shared, volatile state that's not what I want. Yes you can use PyPy, but if that doesn't work for some python framework I use, or if I can't control my deployment environment and it only has CPython I can't use PyPy. Obviously you can write C extensions for about any language, using that as an arguments why the GIL is not a problem for multithreaded Python is disingenuous. Maybe I don't know or don't like to program in C? Green threads are not a substitute for multi-threading either, as they still don't allow full utilization of multiple cores and are really only a solution for I/O bound processing. Of the 'numerous ways to sidestep the GIL' none are satisfactory if you have a CPU bound problem operating on shared state, that lends itself well to parallel execution, which are many. I wouldn't use Python to write a video codec or to do DNA sequence processing for example. It's not a fatal flaw for Python-as-a-language, but it's a flaw of CPython nonetheless, and not an insignificant one.

Posted by w0utert on Mar 24, 2015, 3:33 PM

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>> The GIL is definitely no source of unicorns and rainbows, but I think the case against it is usually overstated.

w0utertMar 24, 2015, 3:33 PM

>> The GIL is definitely no source of unicorns and rainbows, but I think the case against it is usually overstated. There are numerous ways of sidestepping it (multiprocessing, pypy, C extensions, etc.), and it does serve a useful purpose. That's definitely all true, but the article brushes it's implications for multithreaded Python off as if they don't exist, which is what one of the posters above me was probably referring to. Yes you can do multiprocessing, but if I have lots of shared, volatile state that's not what I want. Yes you can use PyPy, but if that doesn't work for some python framework I use, or if I can't control my deployment environment and it only has CPython I can't use PyPy. Obviously you can write C extensions for about any language, using that as an arguments why the GIL is not a problem for multithreaded Python is disingenuous. Maybe I don't know or don't like to program in C? Green threads are not a substitute for multi-threading either, as they still don't allow full utilization of multiple cores and are really only a solution for I/O bound processing. Of the 'numerous ways to sidestep the GIL' none are satisfactory if you have a CPU bound problem operating on shared state, that lends itself well to parallel execution, which are many. I wouldn't use Python to write a video codec or to do DNA sequence processing for example. It's not a fatal flaw for Python-as-a-language, but it's a flaw of CPython nonetheless, and not an insignificant one.

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