Talk:Big O notation

From Wikipedia, the free encyclopedia
Jump to: navigation, search
          This article is of interest to the following WikiProjects:
WikiProject Computing (Rated B-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Computing, a collaborative effort to improve the coverage of computers, computing, and information technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
 
WikiProject Mathematics (Rated B-class, Mid-importance)
WikiProject Mathematics
This article is within the scope of WikiProject Mathematics, a collaborative effort to improve the coverage of Mathematics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Mathematics rating:
B Class
Mid Importance
 Field: Analysis
One of the 500 most frequently viewed mathematics articles.
This article has comments.
WikiProject Computer science (Rated B-class, Top-importance)
WikiProject icon This article is within the scope of WikiProject Computer science, a collaborative effort to improve the coverage of Computer science related articles on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.
 
This article has an assessment summary page.

This is also referred to as "Order Notation"[edit]

eg. f(x)=O(x^2) would be stated as "f(x) has order x squared". It may be a North American way of calling this, but no-one in Australia or Britain ever calls this "Big O Notation". It sounds very childish. We simply refer to this as "Order Notation" which is what the original author called it.

There appears to be some confusion here. "f(x) has order x squared" is usually abbreviated by f(x)\asymp x^2. "f(x)=O(x^2)" has a very different meaning, which could (somewhat unprecisely) be worded as "f(x) is at most of order x squared" (with the understanding that f(x) could very well have an extremely irregular behaviour, with no clear order to speak of. Sapphorain (talk) 08:52, 12 June 2014 (UTC)

Proper way to 'say' Big-O notation[edit]

I am not a native English speaker. I was wondering if this article should mention the proper, or any, way to say Big-O in spoken English. For instance, I don't know which one better: "this algorithm has a Big-O of n squared," "this algorithm has a complexity of n squared," or "this algorithm is n squared."

This discussion seems to be settled here Negrulio (talk) 20:24, 10 June 2014 (UTC)

Algorithms and their Big O performance[edit]

I'd like to put in some mention of computer algorithms and their Big O performance: selection sort being N^2, merge sort N log N, travelling salesman, and so on, and implications for computing (faster computers don't compensate for big-O differences, etc). Think this should be part of this write-up, or separate but linked?

I think separate would be better, to increase the article count :-). Then you can have links from the Complexity, Computation and Computer Science pages. Maybe you can call it "Algorithm run times" or something like that. --AxelBoldt
Or something like analysis of algorithms or Algorithmic Efficiency since you may sometimes choose based on other factors as well. --loh
I'd recommend puting it under computational complexity which earlier I made into a redirect to complexity theory. It should be a page of it's own, but I didn't want to write it ;-) --BlckKnght

Removed polylogarithmic[edit]

Reinstated my VERY bad. Missed a bracket

"Tight" bounds?[edit]

The article refers to terms "tight" and "tighter", but these terms are never defined! Alas, other pages (e.g. "bin packing") refer to this page as the one giving a formal definition of this term; moreover, "Asymptotically tight bound" redirects here. Yes, the term is intuitively clear, but a math-related page should have clear definitions.

I think a short section giving a formal definition of the term "tight bound" and referring to Theta-notation is needed (e.g. as a subsection of section "8. Related asymptotic notations"), and once such a section is created the redirection from "Asymptotically tight bound" should link directly there.