basic thread question

[birdsong]

On Aug 18, 3:18 pm, Derek Martin <c... at pizzashack.org> wrote:
> On Tue, Aug 18, 2009 at 03:10:15PM -0500, Derek Martin wrote:
> > I have some simple threaded code...  If I run this
> > with an arg of 1 (start one thread), it pegs one cpu, as I would
> > expect.  If I run it with an arg of 2 (start 2 threads), it uses both
> > CPUs, but utilization of both is less than 50%.  Can anyone explain
> > why?  
>
> Ah, searching while waiting for an answer (the e-mail gateway is a bit
> slow, it seems...) I discovered that the GIL is the culprate.
> Evidently this question comes up a lot.  It would probably save a lot
> of time on the part of those who answer questions here, as well as
> those implementing solutions in Python, if whoever is maintaining the
> docs these days would put a blurb about this in the docs in big bold
> letters...  Concurrency being perhaps the primary reason to use
> threading, essentially it means that Python is not useful for the
> sorts of problems that one would be inclined to solve they way my code
> works (or rather, was meant to).  It would be very helpful to know
> that *before* one tried to implement a solution that way... especially
> for solutions significantly less trivial than mine. ;-)
>
> Thanks
>
> --
> Derek D. Martinhttp://www.pizzashack.org/
> GPG Key ID: 0x81CFE75D
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I would still watch that video which will explain a bit more about the
GIL.