Intel Fortran Compiler

[Hao He]

Dear friends,

I am trying the Intel Frotran compiler 6.0 for linux on my Pentium 4 Xeon 
based system now. To my simple testing fortran program, which just 
contains some multiplication of float point data, the generated code is 
very fast. However, when I use double precision (real*8) or -r8 option,
I found that the results showed error after the first 8 significant digits. 
When I enforced the -O0 option to disable the default optimizaitions,
the results seemed correct. Unfortunately, the performance droped
a lot, just a little bit faster than g77 (20% or so).

Any one has experience on this prooduct?
My question is: where does the error come from in optimization and
how can I get better performance while not losing precision?
Appreciate for your help.

Best regards,
Hao He