• C

Improving the speed of a C program

Does anyone know a good site which covers improving the execution speed of a C program with register variables, inline functions and the like?

Rob
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rd707Asked:
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nebekerCommented:
Before you go off and start changing variable types (to use "register") and other small-fry type changes, I would suggest that you first profile your application, to find out where the bottlenecks really are.

An excellent (but expensive) tool for this is Quantify from Rational  (http://www.rational.com/products/pqc/index.jsp).

After running the profiler, it will show you the three most important things you need to know before you start optimizing a program:

 * which functions are called the most often
 * which functions are the slowest
 * where your program spends a majority of its CPU time

Once you have this information, you can start digging into the appropriate functions.  But just randomly inlining functions, or changing your variable prototypes aren't going to work...

As the saying goes, 20% of your code does 80% of the work -- so find that 20% before doing anything else.
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rd707Author Commented:
Excellent - many thanks.

rd707
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guidwayCommented:
Glad to be of help. Thanks for the grade!

guidway
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