lammps-5sept release questions about the dump routine.

Hello,

I’m a PhD student in the Systems Group at Georgia Tech working on I/O middleware and I had a couple questions about the LAMMPS code related to the dump routines.

We are trying to use a custom dump procedure that handles multiple processes simultaneously writing to a single file. The header is writing fine, but what we don’t understand is the code between lines 371 and 393 of source file “dump.cpp”. We want buffer_flag to be 0, since we are not writing as on big string.

More specifically, what we don’t understand is the use of clusters, and the variable nclusterprocs.

If someone could shed some light, it would be much appreciated.

Thanks,

Alexis Champsaur

You could look at the src/MPIIO package, which supports multiple procs
writing to a single file for several dump styles.

See dump.h for documentation of many of the variables used in the dump
styles. As the dump doc page explains LAMMPS suports many procs

writing to one file (not simultaneously unless you are using MPIIO), or
one proc per file, or a cluster of procs per file. Nclusterprocs is used
for the latter case.

Steve