Re: [Opensg-users] Expanded use of Boost.Function

[Matthias S. <op...@vr...>]

Hi,

> > Hard to say. We are using AQTime (nice tool by the way) these days
> > to find out what is going on.
>
> But their pricing sucks, charging 3 times more for a floating license
> is ridiculous.

I wouldn't say intel's pricing is much better, but since the base price=20
of AQTime isn't that high.

> > Especially the inlines are very surprising
> > (read frustrating). Most of them are completely ignored EVEN if you
> > use __forceinline. AFAIK inline is something like a hint for a
> > compiler.
>
> inline and __inline in itself yes. But usually there must be a way of
> forcing the compiler to inline. Otherwise the compiler is unusable
> for anything that comes even close to high performance. It's a tool
> so it should never ever have a big impact on the design as long as
> the design is within the language specification, especially if other
> tools prove that it is possible. And it should always listen to the
> programmer who hopefully knows what he/she is doing ;-)

Totally agreed. But, can you still remember the times when the=20
"tuning-community" discovered the register keyword within C ?=20

> >  > > Especially using templates in basic math classes like
> >  > > Vec3f/Pnt3f
> >  > >
> > > > > and so on is probably the worst thing one can do since some
> > > > > functions in OpenSG (like operator+ for Pnt3f) don=C2=B4t get
> > > > > inlined. Not to mention: you loose some chances for
> > > > > optimizations (SIMD for example could be pretty difficult to
> > > > > use in templates when you want to use the same code for
> > > > > Vec2f/Vec3f/Vec4f).
> > >
> > > This is only a half an argument as you can (and always have to)
> > > specialise the SIMD part as there are platforms which do not
> > > support it, e.g. ia64 or ppc platforms. Furthermore in order to
> > > use SIMD for non 128 bit structures you have to
> > > specialise/reorganise on an even higher level like having a
> > > specialised MFVec2f which can handle two two value vectors
> > > combined.
> >
> > Of course you can do template specializations but well then you are
> > going to rewrite most of them anyway :(
>
> not really, comparing the size of a completely (e.g. type, size and
> simd/altivec) unrolled implementation against a templated/specialised
> one I would still say the templated version is  smaller. And more
> important if you have to fix a bug you don't have to trace it through
> n unrolled version.
>
> > Implementing the mentioned
> > specialized 2D case is only useful for very few people I think.
>
> Not unlikely, except if you do a lot of texture coordinate
> computation on the cpu.

not a common scenario I suppose.

> > > > > I finally got used to use my own math classes and do a simple
> > > > > reinterpret cast on values stored in multifields - got me
> > > > > quite some speedup since the compiler does correct inlining.
> > > >
> > > > Do you have some benchmark results you can share? If there is a
> > > > significant impact we need to change things...
> > >
> > > Before we start changing code and design, I would like to verify
> > > if this is a MSVC only problem. If it is I'm tempted to say bad
> > > luck, if they still don't know how to build a proper compiler. I
> > > mean they seem to have managed to add ipo and pgo. Anyway usually
> > > there should be way to force the compiler to inline functions,
> > > something like __forceinline. So before changing code I would go
> > > for that.
> >
> > Sorry, doesn't work.
>
> Can anyone supply some concrete examples, e.g which function and the
> calling place. I really would like to verify it.

We will provide one next week.

Regards

Matthias

=2D-=20
+---------------------+----------------------------+
| VREC GmbH           |                            |
| Matthias Stiller    |                            |
| Robert-Bosch-Str. 7 | tel:    +49 6151 4921034   |
| 64293 Darmstadt     | web:    http://www.vrec.de |
| Germany             | mail:   ms...@vr...         |
+---------------------+----------------------------+