alchemy with multiple SUBSYS bug

marc marcvanh... at
Fri Feb 8 09:22:41 UTC 2013

Can this problem be related to this thread somehow?!searchin/cp2k/Marc$20Van$20Houteghem/cp2k/t5UYWtZt3HI/DlfmK2W-a28J

No succes yet on this matter. I added a big molecular methanol system (128 
molecules) and a small one (2 molecules) that reproduce the problem.  
Important to mention is that the computation only fails when run in 
parallel mode.  It does not occur with a NVT ensemble and/or in serial mode 
(only the combination NPT ensemble and parallel computation fails).  
Probably this is due to the stress tensor implementation.


On Tuesday, November 27, 2012 3:35:51 PM UTC+1, Noam Bernstein wrote:
> Hi - I think I've found a small bug in the alchemy code, and I'm not sure 
> how
> best to fix it. For example for
> there are two calls to mixed_map_forces(), the first with 
> overwrite=.true., the
> second with overwrite=.false.  However, if the first FORCE_ENV has some of
> the atoms missing (e.g. alchemy), the atoms that are missing never have
> their forces overwritten.  Presumably those forces should be set to 0 
> before
> the forces from the second FORCE_ENV are added.  
> Was there some particular reason that the mixed forces aren't all just 
> initialized to 0, 
> and instead the overwrite argument is used?  Because I don't see a 
> reliable way of
> fixing this problem without either some tedious bookkeeping to find
> all atoms that map to nothing in the overwrite=.true. case, or just setting
> all the forces to 0 before the calls to mixed_map_forces().  I'd be happy
> to submit a patch, but if there's some reason it's not a good idea to set
> all the forces to 0, I'd like to understand that.
>            Noam
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