Python and STL efficiency

[Tim N. van der Leeuw]

Mc Osten wrote:
> Tim N. van der Leeuw <tim.leeuwvander at nl.unisys.com> wrote:
>
> > Oh boy; yes indeed the slow python is faster than the fast C++
> > version... Must be something really awful happening in the STL
> > implementation that comes with GCC 3.4!
>
> And the Python version does the very same number of iterations than the
> C++ one? I suppose they are looping on arrays of different sizes, just
> like my "first version".
>

Hmmm.. You're quite right. The C++ version had an array size 100.000
(your version), the Python version still had an array size 10.000 (as
in my modified copy of the original version).

When fixing the Python version to have 100.000 items, like the C++
version, the Python timings are:

Begin Test
Number of unique string objects: 4
so long...
What do you know
fool
chicken crosses road
Number of unique string objects: 400000
so long...
What do you know
fool
chicken crosses road
Fast - Elapsed: 0.512088 seconds
Slow - Elapsed: 1.139370 seconds

Still twice as fast as the fastest GCC 3.4.5 compiled version!

Incidentally, I also have a version compiled with VC++ 6 now... (not
yet w/VC++ 7) .. Compiled with release-flags and maximum optimization
for speed, here's the result of VC++ 6:

LeeuwT at nlshl-leeuwt ~/My Documents/Python
$ ./SpeedTest_VC.exe
Begin Test
What do you know?
chicken crosses road
fool
so long...
What do you know?
chicken crosses road
fool
so long...
Fast - Elapsed: 4.481 seconds
Slow - Elapsed: 4.842 seconds

So you can see that it's 'slow' version of the code is faster than the
'slow' version compiled with GCC, but the 'fast' code is barely faster
than the 'slow' code! And the 'fast' version compiled with GCC is much
faster than the 'fast' version compiled with VC++ 6!

My conclusion from that is, that the vector<> or set<> implementations
of GCC are far superior to those of VC++ 6, but that memory allocation
for GCC 3.4.5 (MinGW version) is far worse than that of MSCRT / VC++ 6.
(And Python still smokes them both).

Cheers,

--Tim



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