Re: [eigen] Issues regarding Quaternion-alignment and const Maps

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

Benoit Jacob wrote:
> 2010/7/9 Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>:
> > Benoit Jacob wrote:
> > > Wow, very good work.
> > >
> > > I indeed confirm the 2x speed improvement, and once i moved your
> > > benchmarking code to a non-inlinable function called from main(), it
> > > even got a bit higher (indeed GCC fails to optimize correctly code in
> > > the main() function).
> > >
> > > Could you make a patch against the development branch? (We're not
> > > going to add features to 2.0 at this point).
> > I think I can do that, but most likely not before Monday/Tuesday.
> >
> > > http://eigen.tuxfamily.org/index.php?title=Developer%27s_Corner#Generating_a_patch
> > >
> > > Also, I didn't know about that loaddup instruction in SSE3. It's
> > > great! I'll have a look at using it in ei_pset1 when SSE3 is
> > > available.
> > It's actually a pity that there is no complete list with *just* all
> > SSE-instructions (not mixed with every other x86-instruction), including a
> > short description, maybe a usage example, and intrinsics for some common
> > compilers. At least I did't find any ...
>
> Yes, I've been trying to see if there is a single-precision equivalent
> for MOVDDUP and I still don't know...


I just searched every <*mmintrin.h> for float and found in <xmmintrin.h>:

/* Create a vector with all four elements equal to *P.  */
extern __inline __m128 __attribute__((__gnu_inline__, __always_inline__, 
__artificial__))
_mm_load1_ps (float const *__P)
{
  return _mm_set1_ps (*__P);
}

but looking at _mm_set1_ps, it doesn't really look like this is actually 
an SSE instruction ...


--
----------------------------------------------
Dipl.-Inf. Christoph Hertzberg
Cartesium 0.051
Universität Bremen
Enrique-Schmidt-Straße 5
28359 Bremen

Tel: (+49) 421-218-64252
----------------------------------------------