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From: Jean-Pierre Flori <jpflori@gmail.com>
Subject: Re: Problem with multiprocessing module from Python
Date: Thu, 31 Oct 2013 18:27:39 +0000 (UTC)
Lines: 59
Message-ID: <l4u7er$2vj$1@ger.gmane.org>
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Le Wed, 30 Oct 2013 10:33:13 +0100, Corinna Vinschen a écrit :

> On Oct 29 21:22, Jean-Pierre Flori wrote:
>> Le Tue, 29 Oct 2013 21:19:14 +0000, Jean-Pierre Flori a écrit :
>> 
>> > Le Tue, 29 Oct 2013 16:59:35 -0400, Christopher Faylor a écrit :
>> >> If you want this fixed, the easiest way to get that to happen is to
>> >> post a simple test case which reproduces the problem.  That is not
>> >> the code snippet that you sent.  A real working example would be
>> >> required.
>> > Sorry about that.
>> > 
>> > Here you go:
>> > """
>> > from multiprocessing import Pool
>> > 
>> > def f(x): return x
>> > 
>> > p = pool(2)
>> > 
>> > p.map(f, [1, 2])
>> > """
>> And I managed to introduce a typo. The third line should read Pool, so
>> it is:
>> """
>> from multiprocessing import Pool
>> 
>> def f(x): return x
>> 
>> p = Pool(2)
>> 
>> p.map(f, [1, 2])
>> """
> 
> Works for me.  I guess.  At least, if I run the script, nothing happens:
> 
>   $ python x.py $
> 
> Same on 32 and 64 bit Cygwin.
> 
> 
> Corinna

I think I got to the bottom of this.
It seems the new implem of sem_getvalue in cgwin1.dll is the cause, see:
http://cygwin.com/ml/cygwin-patches/2013-q3/msg00006.html
It may also explain the random reproducibility if sval stays uninitialized 
or something like that (I did not check it is the case though).

Reverting to 1.7.20 solved the issue on the install I tested.
I guess my previous attempts to downgrade cygwin1.dll were just badly 
done:
I just decompressed the cygwin tarball which only overwrote the dll in /
usr/bin but not in /bin.
Is there a canonical way to do that in a proper way?
Putting it in a local directory and pointing setup.exe ot it?

Best,
JP


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