[Stackless] verify my performance numbers?

Andrew Dalke dalke at dalkescientific.com
Tue Jan 30 03:37:36 CET 2007

On Jan 29, 2007, at 12:13 AM, Santiago Gala wrote:
>  My version substitutes the bloated and hyperlocked Queue class by a
> deque + simple locking, using with for cleaner code.

Interesting.  I didn't think about that because the deque class
doesn't have built-in guarantees that it would be usable across
multiple threads.  It works in CPython because of the implementation
guarantees, but I don't know know if that can be considered portable.

Because the CPython implementation uses a C type and none of the
append or pop calls are re-entrant it works.

> A substantial part of the overhead, thus, is due to the Queue class, 
> though
> stackless is still 50%+ faster than a simple deque+lock solution, plus 
> cleaner code

In checking the analysis I did realize that the thread doing
the pushes onto the Queue/deque (the producer side) can be faster
than the consumer.  I tested it and found that the Queue can have
several thousand pending messages while the stackless version of
course only has one.

Using Queue.Queue(1) nearly doubled the run-time but I need
to verify that.  I got the exception

    Unhandled exception in thread started by
    Error in sys.excepthook:

    Original exception was:

and need to figure out what that means.

Also, the iTunes XML has a reference to a DTD and the expat
parser interface tries to resolve it, so part of the overhead
is doing a network lookup of

					dalke at dalkescientific.com

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