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Bug #46

Constraint or not turned off on slaves

Added by Jelger empty almost 14 years ago. Updated over 13 years ago.

Status:
Closed
Priority:
High
Assignee:
Erik Lindahl
Category:
mdrun
Target version:
Affected version - extra info:
Affected version:
Difficulty:
uncategorized
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Description

If constaints where put on "none" in the mdp file:

Then in /mdlib/update.c :

/* if edyn->bEdsam == FALSE --- this has no effect */
bHaveConstr = bHaveConstr || ed_constraints(edyn);

returns FALSE on the master, but TRUE on the slaves.

This means that the constrainst loops become active on the slaves, which will
interfere with the dynamics.

When T-coupling is used, one temperature group can be both devided on the master
as on the slaves. The total mean temperature of the T-group will be the desired
temperature. However the desired maxwell distribution will be disrupted.

Actually for a homogenous LJ-system I found that the mean temperature on the
slaves is 30 K lower at the desired reference temperature of 300 K than on the
master.

This Bug may have a significant effect on the users of GC-models.

I tested it for the version 3.3, but it may also be present in the older versions.

History

#1 Updated by David van der Spoel over 13 years ago

The edyn struct was not initialized properly before. This has been fixed.

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