Christoph Hormann wrote:
> If your compiler produces a faulty binary with one set of options and a
> working one with a different set that's a bug in the compiler.
Nope, not all code can handle all levels of optimisations well. Lets
assume, for the sake of argument, that Gcc 3.4.3 is stable, since we all
use it ;). Yet I know know numerous programs which can only be compiled
using special flags, or without any Ox-flag at all.

I did some physical modelling with a program called, p3d, which
generated completely different results when compiled with different
settings. This program too, like MegaPov, was dealing with floating
numbers which could differ only in order of magnitude like 1e-7.
Suddenly compiler option are not trivial anymore, although
theoretically, it should be just fine.

> Both the binary version from the website (using -O3 -march=i586) and the
> default options (here: -O3 -ffast-math -malign-double
> -minline-all-stringops -m3dnow -march=athlon-xp -mtune=athlon-xp)
If I run ./configure without options the following flags are produced in
the Makefile:
CXXFLAGS =  -pipe -Wno-multichar -s -O3 -ffast-math -malign-double
-minline-all-stringops -m3dnow -march=athlon-xp -mtune=athlon-xp

Which are exactly the same flags you have.....

Nomail wrote:
> Well, then you have found a kernel bug and should report it to
> the kernel developers.
Always look in the mirror first. Especially if you compile with
"-ffast-math". The compiler generates code which directly accesses the
FPU to perform i.e sin,cos operations en there is no checking for NaN of
Zero; this is responsibility of the programmer. Strange things can &
will happen !!

Anyway, interesting to see that all no-one (!) accepts the possibility
that the MegaPov distribution could contain a error. Although it most
probably does not contain serious bugs, Christoph does a great job here,
 not too many people use it on a linux-box, so there could always be
"something" if compiled on a different Unix-box. Yet all fingers pointed
directly at my hardware, my kernel, my compiler and my dog.

Was the problem itself or did I use foul language ?

So I restate my question: Is anyone using a self-compiled version of
MegaPov and does it run all supplied scenes without trouble ?

I Do !! My Megapov-version is, right now, happily processing,
yet-another-stupid ball-hits-block-animation.

Always willing to help out ;)

Post a reply to this message