[gmx-developers] GROMACS 4.0.1 still broken on Bluegene

Erik Lindahl lindahl at cbr.su.se
Sun Nov 9 22:07:27 CET 2008


On Nov 9, 2008, at 7:41 PM, David van der Spoel wrote:
> I just followed your advice and neither on my Mac nor on a Centos  
> Linux 5.0 box did I get any warnings. Doubtlessly compilers are  
> getting better, but they have come from a very low starting quality.  
> We regularly check compilation in this manner, usually without  
> finding anything beyond the obvious. A new development is that the  
> GNU C library has become more picky with memory management. Due to  
> this some problems in very old code have surfaced (although the code  
> was correct according to the book...). We try to follow the  
> developments, and are grateful for tips like this.

You won't get any warnings by adding -fno-strict-aliasing, as far as I  
know at least :-)

ANSI C actually specifies that no two arrays or pointers that are  
parameters to a function may point to the same memory (unless one of  
them is marked const, if I recall correctly), but the flag above  
relaxes that, which could inhibit some optimization.  However, we've  
been rather careful with this, so I think we adhere pretty close to  
the standard.

Unfortunately some of the issues we've seen with compilers have been  
plain bugs (in the compilers), which takes forever to track down in  
the first place...



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