[gmx-users] CFLAGS

[Joanne Hanna]

Hi

I have recently compiled an mpi version of gromacs 3.2.1 with the icc compiler. I ran into troubles with this error, at the ./configure stage:
* Sorry, these optimization settings don't seem to work for       *
* your C compiler. Use make CFLAGS=..., or edit the top Makefile. *
I decided to use the cflags option -O2.
Can anyone tell me whether this is a good option to use. I understand that -O3 enables more aggressive optimisations such as loop and  memory  access transformation. and is recommended for applications that have loops with heavy use of float-ing point calculations and process large data sets (as from the manual). But i don't know which i should use.
I have been told that optimising too aggressively can produce the wrong numbers.

Anu advice would be much appreciated.

Thanks
Jo


Joanne Hanna
Department of Chemistry
University of Warwick
Coventry
CV4 7AL

J.F.Hanna at warwick.ac.uk