Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Strictly speaking, Big-O <em>doesn't</em> tell you about the growth for numbers you actually use.</p> <p>Big-O notation is about what happens in the limit as the size of the problem (<code>n</code>) tends to infinity. Specific small numbers like 4096 and 8192 are irrelevant to big-O classification. Furthermore, big-O is an <em>upper limit</em>. Bubble sort is O(n^2). It is also O(n^3), and O(n^27), and O(2^n), because all of those functions also provide upper bounds on its running time in the limit. Very loose upper bounds, but bounds nonetheless.</p> <p><em>In practice</em>, many or most algorithms that you'll use, can be observed for realistic values of <code>n</code>, to follow a trend corresponding to their "best" big-O complexity. And that's what you're seeing here - doubling the size quadruples the time, because time is approximately proportional to n^2. Because time is proportional to n^2, the algorithm is O(n^2). The reverse implication does not necessarily hold.</p> <p>People commonly say "bubble sort is O(n^2)", and they mean, "the time taken to bubble sort is proportional to the square of the input size, ignoring a small percentage of special cases which are much faster (already-sorted data in the case of bubble sort)". Both statements are true, but the latter is not what the former actually means, so occasionally it's confusing. Several answers here say the same thing, and they're wrong too as far as the mathematical definition of big-O is concerned. But the incorrect usage is so common that it can't be ignored, presumably because people are informally introduced to big-O classifications of algorithms without ever being taught a formal definition.</p> <p>So, when someone tells you that an algorithm is O(n^2), there's a fairly high probability that what they're <em>trying</em> to tell you is that its worst case is &Theta;(n^2), and if so they might well be further trying to tell you that this trend is observable for the kinds of <code>n</code> you care about. Given this abuse of notation, that's why "O(n^2) algorithms" all become less efficient as you increase <code>n</code>.</p>
    singulars
    1. This table or related slice is empty.
    1. POWhy do O(n^2) algorithms become more inefficient the larger the amount of items it has to sort?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USSteve Jessop
    1. USSteve Jessop
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POWhy do O(n^2) algorithms become more inefficient the larger the amount of items it has to sort?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload