[gmx-users] CFLAGS

Joanne Hanna J.F.Hanna at warwick.ac.uk
Wed Nov 16 14:53:55 CET 2005


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.


Joanne Hanna
Department of Chemistry
University of Warwick

J.F.Hanna at warwick.ac.uk

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