using non-standard optflags (-O3, in particular)
lonely wolf
wolfy at nobugconsulting.ro
Sat Feb 10 04:34:57 UTC 2007
On 02/09/2007 11:22 PM, Patrice Dumas wrote:
> On Fri, Feb 09, 2007 at 03:49:49PM -0500, Simon Perreault wrote:
>
>> Matthew Miller wrote:
>>
>>> How about I include a specific benchmark test in build section that runs
>>> for, say, a minute, and then use that to auto-select between O2 and O3 on a
>>> per-build basis? :)
>>>
>> This is not acceptable because it would make the build nondeterministic.
>>
>
> Yes, but isn't the gain worth this issue? And it shouldn't be that
> nondeterministic or it means that the gain in execution time isn't
> that big.
The test would mean exactly zero for the end user who might have a
completely different architecture. Optimizations which would work great
on a dual-core-with-large cache-machine would probably mean zero or
worse for a standard P4.
What I - as end user - would find useful if I wanted to squeeze the
last bit of performance is a table with benchmarks obtained on different
architectures with different compilation options. But we cannot ship
different packages with N architectures * M compilation options. Or can we?
I think that a valid approach for such an option would be the
application having the same code compiled in with different
optimizations and doing a runtime check to select the fastest one.
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