On 26/06/2010 07:11, John Nagle wrote:
We have just released a proof-of-concept implementation of a new
approach to thread management - "newthreading". It is available
for download at
https://sourceforge.net/projects/newthreading/
The user's guide is at
http://www.animats.com/papers/languages/newthreadingintro.html
The user guide says:
The suggested import is
from newthreading import *
The import * form is considered bad practise in *general* and should not
be recommended unless there is a good reason. This is slightly off-topic
for python-dev, although I appreciate that you want feedback with the
eventual goal of producing a PEP - however the introduction of
free-threading in Python has not been hampered by lack of
synchronization primitives but by the difficulty of changing the
interpreter without unduly impacting single threaded code.
Providing an alternative garbage collection mechanism other than
reference counting would be a more interesting first-step as far as I
can see, as that removes the locking required around every access to an
object (which currently touches the reference count). Introducing
free-threading by *changing* the threading semantics (so you can't share
non-frozen objects between threads) would not be acceptable. That
comment is likely to be based on a misunderstanding of your future
intentions though. :-)
All the best,
Michael Foord
This is a pure Python implementation of synchronized objects, along
with a set of restrictions which make programs race-condition free,
even without a Global Interpreter Lock. The basic idea is that
classes derived from SynchronizedObject are automatically locked
at entry and unlocked at exit. They're also unlocked when a thread
blocks within the class. So at no time can two threads be active
in such a class at one time.
In addition, only "frozen" objects can be passed in and out of
synchronized objects. (This is somewhat like the multiprocessing
module, where you can only pass objects that can be "pickled".
But it's not as restrictive; multiple threads can access the
same synchronized object, one at a time.
This pure Python implementation is usable, but does not improve
performance. It's a proof of concept implementation so that
programmers can try out synchronized classes and see what it's
like to work within those restrictions.
The semantics of Python don't change for single-thread programs.
But when the program forks off the first new thread, the rules
change, and some of the dynamic features of Python are disabled.
Some of the ideas are borrowed from Java, and some are from
"safethreading". The point is to come up with a set of liveable
restrictions which would allow getting rid of the GIL. This
is becoming essential as Unladen Swallow starts to work and the
number of processors per machine keeps climbing.
This may in time become a Python Enhancement Proposal. We'd like
to get some experience with it first. Try it out and report back.
The SourceForge forum for the project is the best place to report
problems.
John Nagle
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/fuzzyman%40voidspace.org.uk
--
http://www.ironpythoninaction.com/
http://www.voidspace.org.uk/blog
READ CAREFULLY. By accepting and reading this email you agree, on behalf of
your employer, to release me from all obligations and waivers arising from any
and all NON-NEGOTIATED agreements, licenses, terms-of-service, shrinkwrap,
clickwrap, browsewrap, confidentiality, non-disclosure, non-compete and
acceptable use policies (”BOGUS AGREEMENTS”) that I have entered into with your
employer, its partners, licensors, agents and assigns, in perpetuity, without
prejudice to my ongoing rights and privileges. You further represent that you
have the authority to release me from any BOGUS AGREEMENTS on behalf of your
employer.
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
