[Stackless] Select() on channels?

Christian Tismer tismer at stackless.com
Sat Sep 15 03:12:04 CEST 2007


Dear Arnar,

> On 9/14/07, Richard Tew <richard.m.tew at gmail.com> wrote:
> ...
>> def alt_select(*channels):
>>     resultChannel = stackless.channel()
>>     # See if anything is already waiting, and if so return it.
>>     for c in channels:
>>         if c.balance > 0:
>>             return c.receive()
> 
> If the alt_select is inside a loop and there's always something
> available on some channel, this will cause starvation of the channels
> that come after that one in the list. The CSP model calls for
> non-determinism here but with a condition that when multiple channels
> have available data, you should give them all an equal probability of
> being selected so in the long run they all get served.
> 
>>     tasklets = []
>>     for inputChannel in channels:
>>         tasklets.append(stackless.tasklet(alt_receiver)(resultChannel,
>> inputChannel))
>>     firstTasklet, firstChannel, result = resultChannel.receive()
>>     for tasklet in tasklets:
>>         if tasklet is not firstTasklet:
>>             tasklet.kill()
>>     return firstChannel, result

Yes, this is true. The LIMBO model seems to assume a global
arbitrator for channels.

I'm very much apart from global structures, at all.

But I don't really understand Arnar's input right now.
Can you please formulate it, again? What is it exactly
what we're missing?

cheers -- chris

-- 
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