Python and STL efficiency

[Tim N. van der Leeuw]

Licheng Fang wrote:
> Hi, I'm learning STL and I wrote some simple code to compare the
> efficiency of python and STL.
>
>
> I was using VC++.net and IDLE, respectively. I had expected C++ to be
> way faster. However, while the python code gave the result almost
> instantly, the C++ code took several seconds to run! Can somebody
> explain this to me? Or is there something wrong with my code?

Hi,

I'm no C++ guru so cannot comment on the C++ code itself, however I do
wonder if you tested your C++ code with other STL implementation such
as gcc (gcc is available on windows as well, in various versions).

What could be is that expanding the list in C++ is done in very small
increments, leading to many re-allocations. Is it possible to
pre-allocate the vector<> with sufficient entries?


Also, your Python code as quoted, doesn't actually call your function
f(). If you say that you get results instantly, I assume that you mean
all 4 strings are actually printed to console?

(I'm surprised that the console prints things that fast).

btw, using range() in Python isn't very efficient, I think... Better to
use xrange().


Asked a C++ collegue of mine to comment, and he strongly suspects that
you're actually running it in the .Net runtime (your C++ code contains
some C#-isms, such as omitting the '.h' in the include <> statements).

Luck,

--Tim