Re: [SLUG] Tuesday afternoon shell command optimisation party!

[Ian Wienand <ianw@xxxxxxxxxxxxxxxxxx>]

On Wed, Dec 19, 2007 at 02:51:34PM +1100, Matthew Hannigan wrote:
> Here's one in lex; ripped off from the flex info page.
> I'd be interested in its performance compared to straight C.
> No doubt worse, just curious how much worse.

Similar to the Python version

ianw@lime:/tmp$ /usr/bin/time ./count < ./randomcommas 
# of commas = 1287100
2.57user 0.02system 0:02.60elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+138minor)pagefaults 0swaps

I'm not even going to guess at what that version is actually doing!  A
quick look says this one is CPU bound, compared to Python which is
memory bound.

Lex
% Cycles lost due to GR/load dependency stalls (lower is better): 0.31

Python
% Cycles lost due to GR/load dependency stalls (lower is better): 46.25

The Python spends a lot of time sitting around waiting for data to
come from the cache/memory (load dependency stalls).  The Lex version
doesn't so the extra time can be attributed to CPU work.

-i