Why is vector array doubled?

Question

Why does the classic implementation of Vector (ArrayList for Java people) double its internal array size on each expansion instead of tripling or quadrupling it?

Answer 1

Personally, I think its an arbitriary choice. We could use base e instead of base 2 (instead of doubling just multiple size by (1+e).)

If you are going to be adding large amounts of variables to the vector then it would be advantageous to have a high base (to reduce the amnt of copying you will be doing.) On the flip side if you need to be storing only a few members on avg, then a low base will be fine and reduce the amount of overhead, hence speeding things up.

Base 2 is a compromise.