From: gminer AT Newbridge DOT COM (Glen Miner)
Newsgroups: comp.os.msdos.djgpp
Subject: Optimization
Date: 27 Nov 1996 13:38:51 GMT
Organization: Newbridge Networks Corporation
Lines: 30
Message-ID: <57hg9b$or5@kannews.ca.newbridge.com>
NNTP-Posting-Host: 138.120.136.238
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

I am currently working on a program that grinds away in a recursive
algorithm tens of thousands of times over a small group of local data. It
doesn't do _any_ io, and only calls a select few functions. Due to the
immense number of calculations required, this is painfully slow. I've
optimized the algorithm a fair amount, and plan to improve it more, but
that is only one part of the optimization process. 

I am currently using the -O3 compile option; is there any other switches I
should be enabling or disabling? I never need to debug the code, so symbol
information is not an issue. 

Can anyone suggest any hard and fast rules for c code optimization under
djgpp? I mean, right now I have a 9x9 array of bytes, and try to index all
of the data in it with pointers. Is this necessary, or is x=MyArray[4][6]
just as good? 

Since this code _is_ a port, I have noticed some data conversion too. An
int is no longer 16 bits long. Since I don't really need a 32 bit int in
the core code would it help at all for me to change things to "short
unsigned int"s?

I may end up doing the heavily used functions in assembler, but I'd like
to make sure that the c code is as optimal as it can be first. Any
comments, suggestions or pointers are welcomed.

Peace
-- 
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