Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!stjhmc!p88.f15.n300.z1.fidonet.org!Lawson.English
From: Lawson.English@p88.f15.n300.z1.fidonet.org (Lawson English)
Newsgroups: comp.sys.mac.programmer
Subject: Pascal deficiency?
Message-ID: <32785.276F7FAE@stjhmc.fidonet.org>
Date: 19 Dec 90 14:50:22 GMT
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Organization: FidoNet node 1:300/15.88 - Tucson Apple Core, Tucson AZ
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Anthony Berno writes in a message to All

AB> Either there is no way to do a quick increment in Pascal, or 
AB> I'm missing something in my knowledge, or I'm wrong about the 
AB> speed difference between things like ++(variable) and 
(variable):=(variable)+1-
AB> 

If your compiler is bad at optimization (and all Apple compilers are 
notoriously
bad), then it won't recognize the special case of inc x for x := x+1;  Of 
course,
as most Apple products are slowed down by the trap dispatcher, thrid-party 
optimization
is pretty much a waste unless a substantial amount of time is spent in 
arithmatic
or searching/sorting.

Consider: the average graphics program on a Plus spends 20% of its time in the
 
trap dispatcher. The average '020 machine spends 60% of its time there. I 
don't
know how much time is spent there in the 030 machines but I would not be 
surprised
if as much as 75-80% of the time is spent there. This assumes that SANE is 
being
used instead of the '881/882. Regions are another area where graphics slows
to a crawl: if you are sure that your program will never write outside of the
screen (you're doing a copybits for instance), set your clip region to a 
rectangle,
rather than let the cute rounded corners of the screen be used. This can speed
 
up full-screen drawing by quite a bit.

My first programming job on the Mac was providing the software 
background/support
for software optimization of the accellerator/graphics board. Some 0f the 
stuff
in the 128k ROMS was pretty scary we found.

Lawson
 

 

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