Re: [Xenomai] Building with hard float: cannot open shared object file libpthread_rt.so.1

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On Thu, Mar 19, 2015 at 01:26:15PM -0400, Lennart Sorensen wrote:
> On Thu, Mar 19, 2015 at 05:48:31PM +0100, Gilles Chanteperdrix wrote:
> > 300 or 1000 instructions are executed in a very short time, not in a
> > 3 milliseconds, otherwise it would mean that each instruction takes
> > 10us or so to execute. Typically, in an ideal situation on a 1GHz
> > processor, an instruction takes 1ns to execute, that is an order of
> > magnitude smaller. So, even if the situation is not ideal, that is
> > still far from the numbers reported by Steve. 
> 
> Well apparently on the Cortex-A8 FPU instructions take 10 or more clock
> cycles to execute, versus 1 in most cases on the Cortex-A9, so 300
> instructions starts to add up.

10 cycles at 1 GHz, is still 10ns, not 10us. That is still 1/1000.

And I do not really believe the cortex a8 is 10 times slower than
the cortex a9, I have benchmarked hand optimized 12x12 matrix
multiplications using doubles (so which can not be implemented with
neon), on both omap3 at 720MHz and omap4 at 1GHz, and I do not
remember such difference between the benchmarks. Maybe A9 is 2 or 3
times faster, but not 10 times.

-- 
					    Gilles.