Optimize Perl
By Martin C. Brown2005-04-11
Putting it All Together
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Now that you know the techniques, here is the way to go about using them together to produce optimized applications. I generally follow this sequence when optimizing:
1. Write the program as optimized as possible using the techniques above. Once you start to use them regularly, they become the only way you program.
2. Once the program is finished or at least in a releasable state, go through and double check that you are using the most efficient solution by hand by reading the code. You'll be able to spot a number of issues just by re-reading, and you might pick up a few potential bugs, too.
3. Debug your program. Bugs can cause performance problems, so you should always eliminate the bugs first before doing a more intense optimization.
4. Run the profiler. I always do this once on any serious application, just to see if there's something -- often obvious -- that I might have missed.
5. Go back to step 1 and repeat. I've lost track of the number of times I've completely missed a potential optimization the first time around. Either I'll go back and repeat the process two or three times in one session, or I'll leave, do another project, and return a few days, weeks, or months later. Weeks and months after, you'll often have found an alternative way of doing something that saves time.
At the end of the day, there is no magic wand that will optimize your software for you. Even with the debugger and profiler, all you get is information about what might be causing a performance problem, not necessarily any helpful advice on what you should do to fix it. Be aware as well that there is a limit to what you can optimize. Some operations will simply take a lot of time to complete. If you have to work through a 10,000-item hash, there's no way of simplifying that process. But as you've seen, there might be ways of reducing the overhead in each case.
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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