Login | Register   
LinkedIn
Google+
Twitter
RSS Feed
Download our iPhone app
TODAY'S HEADLINES  |   ARTICLE ARCHIVE  |   FORUMS  |   TIP BANK
Browse DevX
Sign up for e-mail newsletters from DevX


Tip of the Day
Home » Tip Bank » C++
Language: C++
Expertise: Intermediate
Aug 24, 2004

Using std::vectors Efficiently

Whenever possible, use C++ arrays. Array indexing has an order of magnitude of O(1). This means that it is very fast. However, if the size of the array is not known at compile time, use vectors cautiously. Dynamic allocation in C++ is very costly.

You can reduce the amount of allocations by using the reserve method or specifying an initial capacity in the constructor:


vector<element_type> object_name(initial_capacity);
vector<element_type>::reserve(n);
I consider it good programming practice to always specify an initial_capacity. If the capacity is not known, just specify what the maximum capacity might be. If an initial capacity wasn't specified, then the capacity increases from 512 to 1024 and doubles everytime when more space is needed. This would be a serious mistake, so try to avoid it.

Sophy Pal
 
Comment and Contribute

 

 

 

 

 


(Maximum characters: 1200). You have 1200 characters left.

 

 

Sitemap
Thanks for your registration, follow us on our social networks to keep up-to-date