Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uwmcsd1!leah!itsgw!steinmetz!uunet!super!rminnich
From: rminnich@super.ORG (Ronald G Minnich)
Newsgroups: comp.sys.amiga
Subject: Re: Need info on exceptions
Message-ID: <666@super.ORG>
Date: 29 Aug 88 15:09:03 GMT
References: <3867@louie.udel.EDU>
Sender: uucp@super.ORG
Reply-To: rminnich@metropolis.UUCP (Ronald G Minnich)
Organization: Supercomputing Research Center, Lanham, MD
Lines: 33

In article <3867@louie.udel.EDU> iphwk%MTSUNIX1.BITNET@cunyvm.cuny.edu (Bill Kinnersley) writes:
>Seems to me it depends on what you're computing, Ron.  You're right if
>it's just one variable.
Yes, true if it is one variable you are ok. If it is not, then you
need semaphores. The original question, as i understood it, was
to monitor the progress of a computation, which i assumed would be
indicated by one variable. A proposed way was to use the amiga
equivalent of signal(), since "that's how it was done on Unix".
   I feel very strongly that if you can avoid 
it then don't use interrupts, software or hardware. They are an 
invitation to trouble, and besides, there are much much much better
ways to solve some of these problems on the amiga. 
   I mean, geez, you just do an ObtainSemaphore and a ReleaseSemaphore
and there is one to poll a Semaphore. What more could you ask? 
And they work. 
   Take a look at how people use signals and longjmp() and things on 
Unix. In many cases it is really gross, but there is no other way
because most Unix systems do not even support mmap(), much less 
a simple system such as shmget(). And the way shmem() 
works is real gross. But on the
amiga we can share memory just by sending each other messages. That is 
a wonderful capability. 
   A few years ago an unnamed person at an unnamed company wrote a 
system for IPC that used a high-speed network being developed at Udel.
That network presented hosts with the shared-memory model. The ipc
system allowed you to send messages that contained memory handles.
When i explained that the Amiga IPC already did all this stuff, and
that the network hardware would do well on an amiga, i mostly got
blank stares ("put a network on a game machine?..."). But the 
fact remains that the amiga IPC is well designed and sophisticated,
and well worth using as a way to share memory between several tasks-
something not easily done on Unix. 
ron