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Bug #191

LINCS messages flooding of the logfile if warnangle is set to 180

Added by Martin Hoefling over 11 years ago. Updated over 11 years ago.

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

If lincs_warnangle = 180 or higher (to avoid any lincs related messages), there is still the output of the head of the list.

It (correctly) does not stop the simulation after 10000 steps as fixed in Bug #1.

My intension of setting lincs_warnangle to 180 is to completly turn off lincs warnings in special applications.

History

#1 Updated by Berk Hess over 11 years ago

The LINCS rotations are checked at two places in the code.
During the constraint algorithm this is done assuming a correct
geometry during the iteration/step, which is not correct,
but the (more) correct geometry can only be known after the complete
procedure has been done.
If rotations have been found in this first step, more accurate warnings
are printed in the next step.

lincs_warnangle should not be 90 degrees or more, since a value
of which we need to take 1/sqrt is compared with cos(ang).
I will add a check for this in grompp.

In the code a variable is used which is cos(ang)^2.
So you should try using a value of say 85 degrees instead of 180.

In Gromacs 4.0 there is an environment variable that completely turns
off constraint warnings.

Berk.

#2 Updated by Berk Hess over 11 years ago

I fixed this issue.

grompp will now limit lincs-warnangle to 90 degrees.

When mdrun stops with too many constraint warnings,
it gives a hint that you can set GMX_MAXCONSTRWARN to -1
to turn off constraint warnings.

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