[Squeak-e] adding eventual sending to Croquet'sScriptProcessandScriptScheduler

Robert Withers rwithers12 at attbi.com
Mon Feb 17 08:41:03 CET 2003

On Monday, February 17, 2003, at 04:50 AM, Andreas Raab wrote:

>> what am I missing?
> Simplicity, efficiency and robustness. And a guy named Heisenberg ;) 
> Try it.
> It's the simplest solution since all of the critical invariants are 
> ensured
> primitively. Just think about the scheduler itself - if it were 
> running at a
> higher priority you'd need to tell it when to release the next 
> process. But
> what if 'yer aborted, terminated, killed? How could the scheduler 
> decide if
> there's already a script running? etc. You'd have to communicate too 
> many
> things explicitly that I know for given implictly by the very fact some
> process is currently running.

And I clearly don't know enough yet to really come to a conclusion.  I 
like Heisenberg.  The inability to precisely measure position and 
velocity or time and energy hopefully have something to offer us in the 
world of asynchronous messaging.   It would provide a little leeway in 
exactly when and where an event occurred and was handled.  It's 
probably an emergent property of deadline based scheduling.

I am not sure why you couldn't attach a state machine to the process so 
that it would do the right thing when a scheduler Process asked it to 
reschedule itself.  There looks to be quite a bit of state in 
ScriptProcess already.  Since all scripts are at the same priority, you 
are allowed to do this, right?  If they could have different 
priorities, then you could be interrupted.   What is the low-priority 
scheduler Process?  Is it the ticker?

I am currently more concerned with the lost scripts that I am 
experiencing.  I opened a Process Browser and sure enough, there were 
all my Scripts waiting on Semaphores.  I must have opened up a hole 
somewhere by a) submitting multiple scripts (in a loop) and/or b) not 
signaling a semaphore (or calling some method which does this under the 

I should have the next consolidated package this week sometime.  As we 
discussed, I will include the Scripting changesets, so that it can be 
loaded separately from Croquet.


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