[Radiance-general] Compile error on AMD running Fedora 4

[Ian Tester]

iebele wrote:
> Current rmake command is:
> #!/bin/sh
> exec make "SPECIAL=" \
>         "OPT=-m64 -O3 -mfpmath=sse -DSPEED=200" \
>         "MACH=-Dlinux -D_FILE_OFFSET_BITS=64 -L/usr/X11R6/lib
> -I/usr/include/X11 -DNOSTEREO" \
>         ARCH=IBMPC "COMPAT=bmalloc.o erf.o getpagesize.o" \
>         INSTDIR=/usr/local/bin \
>         LIBDIR=/usr/local/lib/ray \
>         ESUFFIX= \
>         CC=gcc "$@" -f Rmakefile


What version of gcc is installed on your system?
Check using gcc -v

Looking at the man page for gcc-3.4 on my Debian (Athlon XP) system, I'd 
suggest the following settings:

-march=k8	to enable the AMD64 instructions, implies the same
		argument to -mtune.

-msse2		to enable SSE2 instructions. Without this, the -mfpmath=sse
		option is useless.

-mfpmath=sse,387 this will give you a boost if the SSE unit is separate
		from the old x87 unit but I don't know enough about the K8
		architecture to know if it does. It will try to use both
		execution units, but the man page says it still
		experimental.

-ffast-math	the man page says this is dangerous but I've never noticed 		 
any problems myself. Try it if you want.

Apart from that, wait for upcoming GCC-4.x releases to flesh out its 
optimisation features, in particular auto vectorization. The SSE2 
instruction set can handle double precision FP math, better than the single 
precision in SSE or Altivec. You should theoretically be able to get some 
pretty awesome performance out of that processor. Reality is another matter 
though... :(

My other suggestion would be to check out some Gentoo web sites. Those guys 
are nuts about compiler optimisations :P

bye