Neil Cerutti wrote: > On 2006-08-24, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > It will run a lot faster if it doesn't have to keep resizing > > the array. > > I don't see why it should run a lot faster that way. > > Appending elements to a vector with push_back takes amortized > constant time. In the example above, preallocating 40000 strings > saves (probably) math.log(40000, 2) reallocations of the vector's > storage along with the consequent copy-construction and > destruction of some fixed number of strings. Most of those > reallocations take place while the vector is still proportionally > quite small.
Math.log(40000, 2) is not a small number when talking about a relatively expensive operation such as memory allocation and deallocation. And the superfluous copying amounts to probably an extra 2^16 copies in this case - not exactly trivial. -- Ben Sizer -- http://mail.python.org/mailman/listinfo/python-list
