CHARMM Development Project
Posted By: bnumn Generating too many contacts - 06/21/21 07:50 PM
Hi, I am receiving this error message:

***** LEVEL -4 WARNING FROM *****

Based on previous recommendations, I have attempted the following fixes:
1. Increased the size of the PBC
2. Checked that all atoms have coordinates.
3. CHARMM is installed using xxlarge and that the initial message regarding the maximum number of atoms is significantly more than what is in my system.

However, if I change the nonbonded parameters from group based to atom based, the error disappears. I cannot figure out why this is the case. Has anyone encountered this issue before, or might have a clue with regards to the source?
Posted By: lennart Re: Generating too many contacts - 06/22/21 09:41 AM
Please post BRIEF inputs with group and atom based nonbonded parameters. And why do you use BOMLEV -5? Is there an earlier error that eventually leads to this problem?
Posted By: rmv Re: Generating too many contacts - 06/22/21 06:01 PM
The message is from code that sets up the non-bond interaction arrays, and indicates that the system is probably too densely packed. The memory allocated for these arrays is dependent on the atom number limit, but implicitly assumes a particle density. You likely need to repack the system, but you could try increasing the atom limit (CHSIZE) via the command line or the DIMENS statement. If possible, use 'top' in a separate window to monitor the memory usage.
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