----- Original Message ----- 
From: "Igor Stasenko" <siguctua at gmail.com>

>> > This is what i mean. There is a BIG difference between concurrency
>> > (parallel execution with shared memory) and distributed computing.
>> > An 'islands' is fitting good for distributed computing, but does they
>> > fit for concurrent parallel execution? I doubt.
>>
>> Igor, where would you place concurrency with disjoint memories?
>>
>> Would assigning objects to specific processes, within a shared memory, 
>> such
>> that only those processes could mutate that object and the processes were
>> non-interruptable and non-waitable, would that be sufficient to make it
>> disjoint?  Imagine that every object reference (header) was assigned to a
>> specific Vat, and only processes within that Vat could interact with that
>> object.  All msg sends to that object, from other Vats, would be 
>> eventually
>> scheduled with that object's Vat.
>>
>
> Simply because its not scales well. Consider a 1000 and 1 Vats ( 1000
> and 1 tales comes in mind :).
> A 1000 Vats sending a message to the same object, which is scheduled
> in single Vat. So, there will be a HUGE difference in time between
> first sender and last sender when they will receive an answer.
> Yes, for some messages its the only answer, but for other messages,
> like simply asking a state (like accessor), there's no need in
> synchronization, because there's no changes in state and no real need
> in scheduling.
>
> Concept you give is really close to one , which i have in mind. Except
> the example above, which seems will be always a bottleneck.

Ok, so we have coded a bottleneck situation.  It's not a surprise, since we 
have a 1000 objects asking for it's services.  It's time for a refactor and 
remove that bottleneck with some service duplication and load balancing. 
Using promises or futures doesn't remove bad code, just limits the kinds of 
bad code you can have.  This would also be a problem in a distributed 
application that was sending 1000 service requests to a single object.

Regarding accessing some state for a read.  If 2 Vats or Islands are on the 
same processor with shared memory between them and Vat A tries to access the 
state of an object owned by Vat B, as long as there is no relocation 
occurring, we should be able to optimize access to this state with a direct 
memory read operation.  Of course, in Smalltalk we access state owned by an 
object by sending that object a read accessor msg, and I don't see how we 
could determine that a given msg sent was there just for a memory read and 
do the optimization.  It wouldn't surpise me if Exupery might know such 
things.

I'd like to hear some description if the concept you have in mind, if you 
have the time.  What are you thinking about in this arena?

> -- 
> Best regards,
> Igor Stasenko AKA sig.

Cheers,
Rob