Optimize Perl
By Martin C. Brown2005-04-11
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What I've covered here looks entirely at the code that makes up your applications. While that's where most of the problems will be, there are tools and systems you can use that can help identify and locate problems in your code that might ultimately help with performance.
Warnings/strict execution
It's a common recommendation, but it really can make a difference. Use the warnings and strict pragmas to ensure nothing funny is going on with variable use, typos, and other inconsistencies. Using them in all your scripts will help you eliminate all sorts of problems, many of which can be the source of performance bottlenecks. Common faults picked up by these pragmas are ambiguous references and de-references, use of undefined values, and some help identifying typos for unused or undefined functions.
All of this help, though, comes at a slight performance cost. I keep warnings and strict on while programming and debugging, and I switch it off once the script is ready to be used in the real world. It won't save much, but every millisecond counts.
Profiling
Profiling is a useful tool for optimizing code, but all it does is identify the potential location of the problem; it doesn't actually point out what the potential issue is or how to resolve it. Also, because profiling relies on monitoring the number of executions of different parts of your application it can, on occasion, give misleading advice about where a problem lies and the best approach for resolving it.
However, profiling is still a useful, and often vital, part of the optimization process. Just don't rely on it to tell you everything you need to know.
Debugging
To me, a badly optimized program means that it has a bug. The reverse is also true: bugs often lead to performance problems. Classic examples are badly de-referenced variables or reading and/or filtering the wrong information. It doesn't matter whether your debugging technique involves using print statements or the full-blown debugger provided by Perl. The sooner you eliminate the bugs, the sooner you will be able to start optimizing your application.
Tutorial Pages:
» Squeeze the Most From Your Code
» Sloppy Programming, Sloppy Performance
» Approaching Optimization
» Use References
» String Handling
» Loops
» Sorts
» Using Short Circuit Logic
» Use AutoLoader
» Using Bytecode and the Compiler Back Ends
» Other Tools
» Putting it All Together
» Resources
First published by IBM DeveloperWorks
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