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Re: GIL in alternative implementations

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> So I'd like to know: how do these other implementations handle concurrency
> matters for their primitive types, and prevent them from getting corrupted
> in multithreaded programs (if they do) ? I'm not only thinking about python
> types, but also primitive containers and types used in .Net and Java VMs,
> which aren't atomic elements either at an assembly-level point of view.

Well, they definitely have some shortcomings:

test.py:

from threading import Thread
class X(object):
    pass
obj = X()
obj.x = 0

def f(*args):
   for i in range(10000):
       obj.x += 1

threads = []
for i in range(100):
    t = Thread(target=f)
    threads.append(t)
    t.start()

for t in threads:
    while t.isAlive():
        t.join(1)

print(obj.x)

> python test.py
1000000
> pypy test.py
1000000
> jython-2.5 test.py
19217
> ipy test.py
59040

Not that this thing is reasonable to do in real code, but cpython and
other implementations with GIL at least give you some safety margin.

-- 
With best regards,
Daniel Kluev

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Thread

Re: GIL in alternative implementations Daniel Kluev <dan.kluev@gmail.com> - 2011-05-28 13:06 +1100
  Re: GIL in alternative implementations Marc Christiansen <usenet@solar-empire.de> - 2011-05-28 11:55 +0200
    Re: GIL in alternative implementations Wolfgang Rohdewald <wolfgang@rohdewald.de> - 2011-05-28 13:16 +0200
  Re: GIL in alternative implementations John Nagle <nagle@animats.com> - 2011-05-28 09:39 -0700
    Re: GIL in alternative implementations Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-28 17:05 +0000
      Re: GIL in alternative implementations "Gabriel Genellina" <gagsl-py2@yahoo.com.ar> - 2011-06-07 01:03 -0300
        Re: GIL in alternative implementations Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-06-07 07:09 +0000
        Re: GIL in alternative implementations Jean-Paul Calderone <calderone.jeanpaul@gmail.com> - 2011-06-07 05:07 -0700

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