Thanks for the reply. We could resolve this argument if any one of the "low level masters" cares to email me offline [EMAIL PROTECTED], but I'd be open to believe an argument could be made for the context of moving around large amounts of data.
In regards to moving data, SSE/SSE2 is really better suited for code which requires a lot of math like 3d computations. Perhaps the heart of SSE would be the packed multiply and add, where it can do 4 multiplies and 4 adds in one clock cycle (or a half cycle if paired properly). Thus, code which requires heavy math like many of the OSG matrix computations could really benefit from it. I would profile cases like this against hand written assembly since this is what OSG would care about. I looked at the assembly code produced by VS 9 for the optimized matrixf multiply, and I could not have scheduled it better myself by hand. ----- Original Message ----- From: "Gordon Tomlinson" <[EMAIL PROTECTED]> To: "'OpenSceneGraph Users'" <osg-users@lists.openscenegraph.org> Sent: Tuesday, July 29, 2008 2:58 PM Subject: Re: [osg-users] Using SSE within OSG > HI > > I can only go buy our low level masters and their profiling shows that the > hand road asm'ed SSE code is significantly fasted than MS VS compiled code > > Obviously this our experience in our environments and we computationally > heavily and moving and editing terra-bytes of data around in real-time > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of James > Killian > Sent: Tuesday, July 29, 2008 11:38 AM > To: OpenSceneGraph Users > Subject: Re: [osg-users] Using SSE within OSG > > > Sorry... > > I interpreted Gordon's response as follows: > MS does a poor job (insert here with compiling SSE intrinsics), as a result > most of his SSE is asm'ed. > The asm'ed approach is where you don't trust the compiler to do the right > thing with intrinsics, where it has the flexibility of scheduling and > assigning registers etc. > > I disagree with "MS does a poor job compiling intrinsic code", and that you > should not *ever need to resort to __asm anymore. > *this is not absolute, there was once a rare case where we found a strange > anomaly, but later solved by doing an un-intuitive c code change > > >Do you find that MS compilers will produce SSE vectorised code > >_without_ > use of intrinsics or raw __asm? > Ah this is a tricky question. There is in fact an option in VS 8 and VS 9 > project settings to generate SSE or SSE2 code. What this does is that it > will evaluate c code and try to use SSE for it. I was surprised to find > that this actually lowered the performance of c code, especially c code for > matrixf. I'm so glad that the project settings for osg do not turn this on, > and I'd recommend not using that, but instead write intrisics ourselves for > places that need it. > > I hope this clears things up. > > > ----- Original Message ----- > From: "David Spilling" <[EMAIL PROTECTED]> > To: "OpenSceneGraph Users" <osg-users@lists.openscenegraph.org> > Sent: Tuesday, July 29, 2008 10:17 AM > Subject: Re: [osg-users] Using SSE within OSG > > > > James, > > > > > > > I have to disagree, using VS 7 and up to VS 9. > > > > > > Just to clarify - what are you disagreeing with? Do you find that MS > > compilers will produce SSE vectorised code _without_ use of intrinsics or > > raw __asm? > > > > David > > > > > -------------------------------------------------------------------------- -- > ---- > > > > _______________________________________________ > > osg-users mailing list > > osg-users@lists.openscenegraph.org > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
