Re: Comparisons and Benchmarking

Tom Crick <tc@cs.bath.ac.uk> writes:


> [At the level of C and C++, if the various languages don't produce
> programs that are all O(the same) something is seriously peculiar. I
> could imagine, e.g., perl and awk might be different if you use their
> built in hhash tables and your data hashes a lot better in one than in
> the other, but if all your loops and such are explicit, how could the
> performance be different by more than a constant factor? -John]


If the programs allocate and release memory frequently, the
implementation of these operations can dominate the time. And (in spite
of many people's naive expectations), neither allocation of nor freeing
memory are necessarily constant-time operations. Different
implementations of malloc() and free() may have different tradeoffs
(without either being a "bad" implementation), so a particular program
may well have a different big-O complexity with different
implementations of malloc() and free().


You could say that this is not a question of language but of library
implementation, but the distinction between what is a language feature
and what is a library feature is strained at best if all implementations
of a language are required to implement certain standard functions.


Torben
[Good point, libraries can make a huge difference in performance. -John]

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