Hey Stuart, we should coordinate. On Thu, Apr 28, 2016 at 4:11 PM, Stuart Mentzer <osgfo...@tevs.eu> wrote:
> Hi Sebastian, > > > SMesserschmidt wrote: > > Can you elaborate on the specific versions used for the 3rd-party > libraries? Especially if you compiled against Qt and possibly which version. > > > I built against Qt 5.6 and osgQt was built. I used the latest version of > dependencies: > curl 7.48.0 > freetype 2.6.3 > giflib 5.1.4 > glut 3.7 > libjpeg 9b > libpng 1.6.21 > libtiff 4.0.6 > minizip GitHub tip > zlib 1.2.8 > > > > Interesting, can you point to some sources why the /fp:fast is needed > > for auto-vectorization? I'm pretty sure I've seen at least SSE2 > > vectorization on some meta-programming matrix code of mine. Precision > > is a real issue for me, so forgive my skepticism. > > > Yes, it is hard to find the documentation on this. The "fast" option is > required for floating point loops to fully auto-vectorize because > vectorization can reorder operations, thus breaking strict IEEE rules. > Similarly, if you put #pragma simd on a loop it will enable "fast" for you. > A reference for this with VC++ is: > > https://blogs.msdn.microsoft.com/vcblog/2015/10/19/do-you-prefer-fast-or-precise/ > (see A7. Auto-Vectorization) > For Intel C++ one reference is the comment by Tim P. (who knows Intel > compilers) in: > https://software.intel.com/en-us/forums/intel-c-compiler/topic/508146 > where he says "/fp: options other than fast prevent vectorization which > depends on optimizing order of operations" > > It is probably most accurate to say that some vectorization is possible > without the "fast" options but avoiding associativity limits vectorization. > I'm not sure if /fp:fast=1 gives the full auto-vectorization with less > precision loss. It would be good to have an option that allows reordering > for loop vectorization but still uses the full precision math library > calls, but I don't think that exists. I get the sensitivity to precision, > which is why I'm trying to indicate that this first Intel C++ build is sort > of experimental. Once we give it a workout and see the positive and > negative effects of various options we'll know better what build variations > are worth providing. > > Regards, > Stuart > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=67017#67017 > > > > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > -- Chris 'Xenon' Hanson, omo sanza lettere. xe...@alphapixel.com http://www.alphapixel.com/ Training • Consulting • Contracting 3D • Scene Graphs (Open Scene Graph/OSG) • OpenGL 2 • OpenGL 3 • OpenGL 4 • GLSL • OpenGL ES 1 • OpenGL ES 2 • OpenCL Legal/IP • Code Forensics • Digital Imaging • GIS • GPS • osgEarth • Terrain • Telemetry • Cryptography • LIDAR • Embedded • Mobile • iPhone/iPad/iOS • Android @alphapixel <https://twitter.com/alphapixel> facebook.com/alphapixel (775) 623-PIXL [7495]
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