[Numpy-discussion] String sort

Francesc Altet faltet@carabos....
Sat Feb 9 15:29:07 CST 2008


One more thing on this.  I've been doing some benchmarking with my 
opt_memcpy() macro in the quicksort_string function, and I should say 
that while it is definitely more efficient than my system memcpy for 
small values of n (the number of bytes to copy), this doesn't keep true 
for all values of n.  For example, for n<16, opt_memcpy() can be more 
than 4x faster than system memcpy (and this is why I naively thought 
that it would be faster in general).  However, for n>80, memcpy beats 
opt_memcpy between a 25% and 100% (depending on whether n is divisible 
by 2, 4 or 8).  This is on my Linux system (Ubuntu 7.10), but perhaps 
with Windows the behaviour can be different.

I think I would be able to come up with a routine that can offer a 
balance between opt_memcpy and system memcpy, but that should take some 
time.  So, until I (or anybody else) do more research on this, I think 
it would be safer if you use system memcpy for string sorting in NumPy.


>0,0<   Francesc Altet     http://www.carabos.com/
V   V   Cárabos Coop. V.   Enjoy Data

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