On Feb 13, 2008 10:56 AM, Francesc Altet <
faltet@carabos.com> wrote:
A Wednesday 13 February 2008, Charles R Harris escrigué:
> OK,
>
> The new quicksorts are in svn. Francesc, can you check them out?
>
Looks good here. However, you seem to keep using your own copy_string()
instead of plain memcpy(). In previous benchmarks, I've seen that
copy_string() is faster than memcpy only for small values of the length
of the block to be copied.
Yes, I noticed that your benchmark program crossed over to using memcpy at 16 chars, and I will probably add that feature. I was being conservative to start with.
<snip>
Finally, you also will have noticed the indirect sort line in the plot.
This is because I was curious about when this method would win a direct
sort. And, by looking at the plot, it seems that the crosspoint is
around strings of 128 bytes (much more in fact that I initially
thought), and starts to be very significant (around 40% faster) at 256
bytes. So perhaps it would make sense to add the possibility to choose
the indirect method when sorting those large strings. This, of course,
would require more memory for the indices, but using 4 or 8 additional
bytes (depending if we on 32-bit or 64-bit), when each string takes 200
bytes, doesn't seem too crazy. In any case, it would be nice to
document this in docstrings.
It would be easy to add this feature, but for the moment I think the best thing is to document it.
Another fairly easy change that could be made is to support strided arrays. That might speed sorting of non-contiguous arrays and sorts on axis other than -1. The only reason it isn't there now is that I originally wrote the sorting routines for numarray and numarray's upper level interface passed contiguous arrays to the sort functions.
Be warned, I'd like to stress out that these are my figures for my _own
laptop_. It would be nice if you can verify all of this with other
achitectures (your Core2 machine seems different enough). I can run
the benchmarks on Windows (installed in the same laptop) too. Tell me
if you are interested on me doing this.
Its easy enough to test if you compile from svn, just add your new copy function and change the name in this line:
#copy=copy_string, copy_ucs4#
to use your function instead of copy_string.
Chuck