When is performance gain significant enough to implement that optimization?

Asked 2010-03-23T00:37:21.643

following the text book, I do measure performance whenever I try optimizing my code. Sometimes, however, the performance gain is rather small and I can't decisively decide whether I should implement that optimization.

For example, when a fix shortens an average response time of 100ms to 90ms under some conditions, should I implement that fix? What if it shortens 200ms to 190ms? How many condition should I try before I can conclude that it will be beneficial overall?

I guess it's not possible to give a straight forward answer to this, as it depends on too many things, but is there a good rule of thumb that I should follow? Are there any guideline/best-practices?

EDIT:Thanks for the great answers! I guess the moral of the story is, there is no easy way to tell whether you should, but there ARE guidelines that can aid that process.. Things you should consider, things you shouldn't do etc. This particular time I ended up implementing the fix, even though it made a few line of code into 20-30 lines of code. Because our app. is very performance critical, and it was a consistent 10% gain in various realistic cases.

performance language-agnostic optimization

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3 Answers

The only sensible approach to your question is something along the lines of "when the benefit is large enough to warrant the time you invest in exploring, implementing and testing the optimization."

The "benefit is large enough" is extremely subjective. Can you or your employer sell more units of software if you make this change? Will your user base notice? Will it give you personal gratification to have the fastest-possible code? Which of those or similar questions apply is something only you can know.

By and large, most of the software I have written (in a 20+ year career) has been "fast enough" out of the box, and the code I cared to optimize presented itself as an obvious bottleneck to the end users: Queries taking a long time, scrolling too slow, that sort of thing.

answered 2010-03-23T00:44:03.847

Is the optimization obfuscating your code too much?
Do you really need an optimization? if your app just runs fine then readability of the code is probably more important
Did you work on the general design and algorithms of your application before trying small hacky optimizations?

answered 2010-03-23T00:44:15.137

If the performance gain is small, consider the other factors: maintainability, risk of making the change, understandability, etc. If it reduces the ability to maintain or understand the code, it probably isn't worth doing. If it improves those attributes, then it's more reason to implement the change.

answered 2010-03-23T00:45:16.120

When is performance gain significant enough to implement that optimization?

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