g77, g95, optimization

[Tobias Burnus]

Hi,

Sternbach, William wrote:
> 2) What is the current status of g95 - Is it stable or is it still
> considered beta.
>   
Note: There are two compilers "gfortran" which is since GCC 4.0.0 part
of the normal GCC and g95 (http://g95.org) which is based on GCC but not
included in GCC. Both gfortran and g95 are usable and are used for
production. (Though like all software they are not completely bug free.)

gfortran 4.0.x I would consider too buggy to be used. gfortran 4.1.3
works rather well though gfortran 4.2.0 might be better suited for
production use (4.2 contains extra bugfixes and additional features such
as OpenMP or allocatable components; additionally it is faster).

The developer version gfortran 4.3 contains fewer Fortran bugs but might
be from time to time a bit unstable if some change in the middle end or
in the Fortran part has a regression. None the less, we have presumably
over thousand of downloads every month and most of the time 4.3 works well.

Binaries of GCC/gfortran can be found at:
http://gcc.gnu.org/wiki/GFortranBinaries

Benchmark on Athlon64:
http://physik.fu-berlin.de/~tburnus/gcc-trunk/benchmark/#rt

> 3) I have a PC with an Intel Core 2 Duo E6700 CPU which runs at 2.66
> Ghz.
>    Could anyone recommend any compiler options which will cause
> optimized code generation
>    for this CPU.
>   
Using GCC 4.x I would use:  -march=nocona -ffast-math -funroll-loops -O3
-msse3 -ftree-vectorize
Depending on you code, you may or may not use -ffast-math as it contains
some "unsafe" math optimizations, see also:
http://gcc.gnu.org/wiki/GeertBosch

Tobias