On Mon, Nov 19, 2012 at 1:05 PM, David Henningsson <di...@ubuntu.com> wrote:

> Given that floats are faster on ARM devices (and probably older x86
> devices as well), I think it makes sense to switch back to using single
> point precision by default.


I don't really care too much. Double precision needed real world testing in
the past, and now I'm confident enough with it. We may want to suggest in
the build system different optimal defaults for each architecture instead a
single default for all. This is non-trivial because issues
like cross-compiling, usual for ARM development.


>  Automatic denormals to zero doesn't prevent FP operations being slower
>> when
>> such numbers are involved. The problem is the larger CPU usage if there
>> are FP
>> exceptions, which happens in all CPUs except modern Intel processors.
>>
>
> I'm trying to verify this theory,


I'm not sure which part you don't buy: that there are still some problems
with denormals or other FP exceptions in the DSP code? or that denormals
are a problem in most architectures?  The former is pretty easy: the FPE
check build option as I suggested. The latter is pretty well documented on
the Net, I think.


> Maybe it's something else, like cache misses or so?


Sure, there may be several additional factors. In my opinion, a good
strategy is to walk one step at a time.

Regards,
Pedro
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