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From: ali@rocky.STANFORD.EDU (Ali Ozer)
Newsgroups: comp.sys.mac
Subject: Re: Mac Multitasking
Message-ID: <496@rocky.STANFORD.EDU>
Date: Sun, 16-Aug-87 12:59:50 EDT
Article-I.D.: rocky.496
Posted: Sun Aug 16 12:59:50 1987
Date-Received: Sun, 16-Aug-87 22:45:40 EDT
References: <6565@eddie.MIT.EDU> <2742@hoptoad.uucp> <3638@cit-vax.Caltech.Edu> <2758@hoptoad.uucp>
Reply-To: ali@rocky.UUCP (Ali Ozer)
Organization: Stanford University Computer Science Department
Lines: 63

In article <2758@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes:
>Well, as long as the downloading loop cedes control of the processor every
>time through, a trivial code change, then synchronous multitasking will
>serve this end quite well. ...
>   I don't think you understand the Mac
>very well, frankly.  You don't need time-slicing with a notebook and pen,
>and for 95% of the things on the Mac you don't need it, either.  For the
>remaining 5%, MultiFinder makes it pretty easy to write them so they can run
>in the background, even in current versions.  No coroutines, asynchronous
>notifications, or other weird code structures, just periodically giving up
>control of the processor.  For something like a download or save, it ought
>to be nearly trivial.  For computation-intensive processing, presumably you
>don't want to slow things down to that extent anyway, whether through
>synchronous or asynchronous interruptions.

I think I understand the Mac, so I will reply to this one...

The multitasking we Amiga users talk about is the kind of 
multitasking that sits there waiting for you to need it. It's not the
kind of multitasking that the programmer or the user has to
prepare for. Any computer (even the C64) can be made to print in the 
background, but no programmer of user will take the time to do all the work,
because it requires extra effort. Same with most Mac user's attitude towards
multitasking --- They think it requires extra work, or means your programs
will run twice as slow...

Right now, as I'm typing this, I'm running VideoScape 3D, a *computationaly
expensive* 3D graphics program. When I started running the program, I had
no intention of reading news. But then I decided to create a 100-frame
animation, and a pretty hairy one, one that's going to take about 20 minutes.
After watching it go through the first 3 frames, I decided it was a waste
of time, so I simply went to my CLI window and ran VT100, and here I am.
VideoScape is running at priority -5, while VT100 is running at 0, so 
I feel absolutely no slowdown it my typing. But, VideoScape is already at
frame 40, so it's running fine. Maybe a few percent slower, but hey, I got
to browse through comp.sys.mac in the meantime, not an easy feat!
(And when I say "few percent," I do mean 2 or 3 percent, not 20 percent.
Amazing how little CPU typing requires.)  

I did not need to "change a few lines in my code," nor I did not need to
decide before had that I was going to run VT100 during VideoScape.

Then there's the programmers life. Think how much better Mac programs
would be if you had multitasking. Those convoluted loops to get events!
How you have to make sure everything gets done everytime through your loop.
How CPU-intensive routines seem to step on user's input! Etc..
With "true" multitasking, an ordinary program can start up any portion
of itself (say a function or a procedure) as a seperate task. The code
is not duplicated, it just starts running as a task which either dies when
the parent things it's had enough of a life, or when it hits its
end. Just think about it, Mac programmers, if you had that ability, how
much better your programs would look and how much better you would feel
not having to do convoluted things... And to the person who said "you
don't need messages in a graphics environment" --- well, what better way to 
get the tasks in a situation like this talking? 

I appreciate Apple's effort in trying to get the Mac to multitask --- what
I don't understand is how they call these current attempts (like the
Switcher and now the Multifinder) "multitasking". 

Ali Ozer, ali@rocky.stanford.edu

[Wow I'm upto frame 62.]