diff --git a/doc/src/Errors_warnings.rst b/doc/src/Errors_warnings.rst index ceccc0b74c..306c9b7b31 100644 --- a/doc/src/Errors_warnings.rst +++ b/doc/src/Errors_warnings.rst @@ -118,6 +118,24 @@ Doc page with :doc:`ERROR messages ` incorrect periodic images of atoms in interaction lists. To avoid, either use :doc:`pair style zero ` with a suitable cutoff or use :doc:`comm_modify cutoff `. +*Communication cutoff is shorter than a bond length based estimate. This may lead to errors.* + + Since LAMMPS stores topology data with individual atoms, all atoms + comprising a bond, angle, dihedral or improper must be present on any + sub-domain that "owns" the atom with the information, either as a + local or a ghost atom. The communication cutoff is what determines up + to what distance from a sub-domain boundary ghost atoms are created. + The communication cutoff is by default the largest non-bonded cutoff + plus the neighbor skin distance, but for short or non-bonded cutoffs + and/or long bonds, this may not be sufficient. This warning indicates + that there is an increased risk of a simulation stopping unexpectedly + because of Bond/Angle/Dihedral/Improper atoms missing. It can be + silenced by manually setting the communication cutoff via + :doc:`comm_modify cutoff `. However, since the + heuristic used to determine the estimate is not always accurate, it + is not changed automatically and the warning may be ignored depending + on the specific system being simulated. + *Communication cutoff is too small for SNAP micro load balancing, increased to %lf* Self-explanatory. diff --git a/src/comm.h b/src/comm.h index d308a26367..1743436e22 100644 --- a/src/comm.h +++ b/src/comm.h @@ -253,6 +253,22 @@ be generated and LAMMPS may lose atoms or use incorrect periodic images of atoms interaction lists. To avoid, either define pair style zero with a suitable cutoff or use comm_modify cutoff. +W: Communication cutoff is shorter than a bond length based estimate. This may lead to errors. + +Since LAMMPS stores topology data with individual atoms, all atoms comprising +a bond, angle, dihedral or improper must be present on any sub-domain that +"owns" the atom with the information, either as a local or a ghost atom. The +communication cutoff is what determines up to what distance from a sub-domain +boundary ghost atoms are created. The communication cutoff is by default the +largest non-bonded cutoff plus the neighbor skin distance, but for short or +non-bonded cutoffs and/or long bonds, this may not be sufficient. This warning +indicates that there is an increased risk of a simulation stopping unexpectedly +because of Bond/Angle/Dihedral/Improper atoms missing. It can be silenced by +manually setting the communication cutoff via comm_modify cutoff. However, +since the heuristic used to determine the estimate is not always accurate, it +is not changed automatically and the warning may be ignored depending on the +specific system being simulated. + UNDOCUMENTED U: OMP_NUM_THREADS environment is not set.