premature-optimization | 易学教程

When is optimization premature? [closed]

阅读更多关于 When is optimization premature? [closed]

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . I see this term used a lot but I feel like most people use it out of laziness or ignorance. For instance, I was reading this article:

What is the Cost of Calling array.length

阅读更多关于 What is the Cost of Calling array.length

While updating for loops to for-each loops in our application, I came across a lot of these "patterns": for (int i = 0, n = a.length; i < n; i++) { ... } instead of for (int i = 0; i < a.length; i++) { ... } I can see that you gain performance for collections because you don't need to call the size() method with each loop. But with arrays?? So the question arose: is array.length more expensive than a regular variable? jjnguy No, a call to array.length is O(1) or constant time operation. Since the .length is(acts like) a public final member of array , it is no slower to access than a local

What is the Cost of Calling array.length

阅读更多关于 What is the Cost of Calling array.length

问题 While updating for loops to for-each loops in our application, I came across a lot of these \"patterns\": for (int i = 0, n = a.length; i < n; i++) { ... } instead of for (int i = 0; i < a.length; i++) { ... } I can see that you gain performance for collections because you don\'t need to call the size() method with each loop. But with arrays?? So the question arose: is array.length more expensive than a regular variable? 回答1: No, a call to array.length is O(1) or constant time operation.

When is optimisation premature?

阅读更多关于 When is optimisation premature?

问题 As Knuth said, We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. This is something which often comes up in Stack Overflow answers to questions like \"which is the most efficient loop mechanism\", \"SQL optimisation techniques?\" (and so on). The standard answer to these optimisation-tips questions is to profile your code and see if it\'s a problem first, and if it\'s not, then therefore your new technique is unneeded. My