[Ffmpeg-devel] int vs. float: Hard Numbers

Michael Niedermayer michaelni
Fri May 20 21:27:52 CEST 2005


On Friday 20 May 2005 21:17, Mike Melanson wrote:
> Michael Niedermayer wrote:
> > if it where so simple ...
> > but it isnt, the code is flawed and wont tell you much usefull
> > the first problem is that its all executed just once, so the code wont be
> > in the code cache, practically no speed critical piece of code would be
> > executed just once ...
> 	Could we mitigate this problem by "warming up" the cache by running the
> function 1000 times and then profiling run #1001?

should be ok

> > the second problem is that every instruction uses the result of the
> > previous, while this gives one interresting value for comparission we
> > should also meassure how fast cpus are if the instructions dont depend
> > upon each other
> 	I wanted to stay away from memory accesses, naturally. So, how about a
> series of instructions that rotated between using different registers so
> that the CPU could perhaps re-order the instructions during execution?

should be ok too, or simpler just dont use the result


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