[Bug libstdc++/40852] parallel sort run time increases ~10 fold when vector size gets over ~4*10^9

["jaffe at broadinstitute dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #2 from jaffe at broadinstitute dot org  2009-07-24 20:43 -------
Subject: Re:  parallel sort run time increases ~10 fold
 when vector size gets over ~4*10^9

If instead of sorting a vec<int>, one sorts a vec<long long>, there is still a
ten-fold
slowdown, as one increases the vector size from 4 to 5 billion.  So it's not
the total
amount of memory that matters, but rather the number of entries in the vector. 
I don't
think this is about cache effects.

Best,

David

============================================================================================

rguenth at gcc dot gnu dot org wrote:
> ------- Comment #1 from rguenth at gcc dot gnu dot org  2009-07-24 20:29 -------
> I suppose you are running into cache effects.  Why do you think this is a GCC
> bug?
> 
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40852