[gmx-users] There is no domain decomposition

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Dear users,

I get "domain decomposition error" in the energy minimization step of an
apo-protein. The last part of the log file is below.

log file:
...
Initializing Domain Decomposition on 24 ranks
Dynamic load balancing: no
Will sort the charge groups at every domain (re)decomposition
Initial maximum inter charge-group distances:
    two-body bonded interactions: 5.122 nm, LJ-14, atoms 3888 3896
  multi-body bonded interactions: 0.422 nm, Proper Dih., atoms 3888 3896
Minimum cell size due to bonded interactions: 5.634 nm
Guess for relative PME load: 0.18
Will use 18 particle-particle and 6 PME only ranks
This is a guess, check the performance at the end of the log file
Using 6 separate PME ranks, as guessed by mdrun
Optimizing the DD grid for 18 cells with a minimum initial size of 5.634 nm
The maximum allowed number of cells is: X 1 Y 1 Z 1

-------------------------------------------------------
Program mdrun_mpi, VERSION 5.0.5
Source code file:
../gromacs/5.0.5/src/gromacs-5.0.5/src/gromacs/mdlib/domdec.c, line: 6902

Fatal error:
There is no domain decomposition for 18 ranks that is compatible with the
given box and a minimum cell size of 5.63385 nm
Change the number of ranks or mdrun option -rdd


After I got that error, I tried -dd  3 3 2 -npme 6 options with mdrun. This
times I got the following error:

Fatal error:
The initial cell size (3.047267) is smaller than the cell size limit
(5.633849), change options -dd, -rdd or -rcon, see the log file for details
For more information and tips for troubleshooting, please check the GROMACS

Later I used -rdd 0.7 option with mdrun but it didn't help also. Lastly I
excluded some bonds that have long distance (for instance: 5.122 nm, LJ-14,
atoms 3888 3896) in itp file but it couldn't fixed the problem.

Could you give me any clue about how to solve the error?

-- 
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