On Thu, 16 Jun 2011, Roy Stogner wrote:
On Thu, 16 Jun 2011, John Peterson wrote:
On Thu, Jun 16, 2011 at 10:43 AM, Roy Stogner <[email protected]>
wrote:
What compiler and flags are you using? It looks like the real
optimization you need here is a change in one or both of those!
GCC 4.2.1, -O3
And now we know which one you need to change. ;-)
Hmm... I should make this clearer:
I'm actually still okay with switching from std::fill to memset() in
our zero() functions (a few percent faster on the already-fastest
compiler options is nothing to sneeze at), even if it'll be a much
more minor optimization than you'd expect in most cases and a slight
pessimization in others.
I'm just saying that, even if we do make the switch, you should
upgrade your compiler too. If it flubbed std::fill that badly then
there's probably lots of other stuff it's not optimizing as well as it
should be.
It'd be nice to do a change like this ATLAS-style, where we test
performance at configure-time and pick what to use... not sure if
that's safe for casual use, though; I'd hate to get a grossly
suboptimal option just because I happened to be running another
process that interfered with timing while the optimal implementation
was being tested.
---
Roy
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