Lots of concurrency

Jecel Assumpcao Jr jecel at merlintec.com
Fri Oct 26 06:35:24 UTC 2001


On Thursday 25 October 2001 13:01,  Ken Kahn wrote:
> I think her problem is that her model of programming is sequential as
> a result of her year of Logo programming. [...]

I agree 100%. There is no way that she would have come up with a time 
slicing solution if she hadn't been taught to use it in these kinds of 
situations. Check out the cover of the Logo issue of Byte magazine 
(August 1982): it is a listing for a program where the single turtle is 
time sliced to simulate four turtles.

> [3 bears definition of asynchronous]
>
> These problems with asynchronous messages don't match my experience.
> Maybe these problems are completely a consequence of mixing
> asynchrony and sequential programming.

Exactly - these happened in the context of people using C tools on the 
Transputer (I used Occam or assembler instead). With synchronous 
messages you get an automatic send/receive order on the client (since 
sending implies waiting for a reply) and receive....send on the server 
(in the case where receiving is implicit and follows automatically 
after sending the reply to the previous messages).

With assynchronous messages I saw a lot of send/send or receive/receive 
bugs in other people's code though it was never a problem for me. Note 
that you can have the exact same problems with Occam's kind of 
synchronous messages. Hmmm... perhaps I should have talked about "one 
way" and "two way" messages instead?

-- Jecel




More information about the Squeak-dev mailing list