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 12:43:26PM -0400, Lennart Sorensen wrote:
> On Thu, Mar 19, 2015 at 05:04:03PM +0100, Gilles Chanteperdrix wrote:
> > My point was, there may be some pathological values that may involve
> > using expm1 or logp1 instead of log or exp, and so to avoid pow
> > entirely. Also, I am not sure pow optimizes the case where b is an
> > integer. It would be interesting to know the actual values of a and
> > b which cause pow to explode.
> 
> Could be.
> 
> For fun I checked how many instructions it took to execute 
> pow(1.234000,12.200000) to get 13.003041 and according to my gdb run,
> it took 1151 instructions.  Now I did not enable optimization for that
> build, which might matter.  Those were of course not all floating pointer
> instructions, but quite a few of them are.
> 
> With -O3, it dropped to 303 instructions.
> 
> I should try the same test on armel to see what difference it shows just
> because I am curious.  I would have to setup an armel chroot to run
> in first.

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. 

So, again, it would be interesting to know the actual values Steve
has that cause pow to go crazy.

-- 
					    Gilles.