Re: [Caml-list] O'Caml vs C++: a little benchmark

[Markus Mottl <markus@oefai.at>]

On Sun, 18 Aug 2002, Oleg wrote:
> Firstly, I expected iteration over O'Caml lists and integer arrays to
> be as 
> fast as iteration over std::list and std::vector<int>, respectively.
> Instead, > the benchmark gave me a speed difference of about 10x and
> 100x in favor of 
> C++ for lists and arrays, respectively.

My timings differ considerably (AMD Athlon 800 MHz 256 MB RAM; g++-2.96; 
demo_all.sh instead of demo_all_root.sh):

  lists
  0.680
  1.030
  2.740
  arrays
  0.250
  3.190
  rev
  0.200
  0.070
  memory
  0.840
  2.120
  tree
  7.280
  8.810

Note, btw., that I have measured user time: real time, which you have
chosen is just too unstable on my machine. Maybe this explains some of
your extreme measurements. I have also used a different file for reversal
(/etc/termcap) and have not run things with your root-script.

OCaml never inlines and/or unrolls recursive functions, giving iterative
solutions in C++ a significant edge concerning optimizations. The same
is true for the array solution, where you are even using higher-order
functions with "fold_left".

> Secondly, a little benchmark comparing mutable binary trees of 64 bit
> floats also showed g++-3.2 to be about an order of magnitude faster.

Not on my machine / with my compiler. Btw., not very fair of you to 
compare ephemeral and persistent datastructures... ;-)

> What was even more surprising was that O'Caml turned out to be about
> 10 times > faster than C++ for reversing lines in a file. I did not
> use explicit buffers > of any kind in either version, and in C++
> program, I used "getline", reading 
> into std::string which should provide about the same level of
> abstraction and > overflow protection as O'Caml string.

Because the C++-iostream library just sucks (at least the implementation 
used by g++). OCaml-I/O as provided by the Pervasives-module is way 
faster.

> I'm curious as to where these huge differences for these small
> programs come from.

Look at the assembler output for details... ;-)

Regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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