Is std::vector so much slower than plain arrays?

Question

I\'ve always thought it\'s the general wisdom that std::vector is \"implemented as an array,\" blah blah blah. Today I went down and tested it, and it seems to

Answer 1

In my experience, sometimes, just sometimes, vector can be many times slower than int[]. One thing to keep mind is that vectors of vectors are very unlike int[][]. As the elements are probably not contiguous in memory. This means you can resize different vectors inside of the main one, but CPU might not be able to cache elements as well as in the case of int[][].