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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
nthreads command :h3
[Syntax:]
nthreads n :pre
n = # of threads to be used per MPI task :ul
[Examples:]
nthreads 1
nthreads 6
nthreads * :pre
[Description:]
Specify how many threads are to be used per MPI task in a hybrid MPI/multi-threading environment.processors are mapped as a 3d logical grid to the global
simulation box.
When this command has not been specified, LAMMPS will choose n according
to the defaults of the threading environment, e.g. in OpenMP according to
the OMP_NUM_THREADS environment variable or using all available processors
if that is not set.
For a package like LAMMPS, threading is typically not as efficient as
a distributed data parallelization via domain decomposition using MPI
message passing. Thus this keyword is mostly of use when MPI parallelization
is becoming inefficient, e.g. when using a "slow" network (like GigE with
TCP/IP) or when reaching the limit of scaling.
[Restrictions:]
This command cannot be used after the simulation box is defined by a
"read_data"_read_data.html or "create_box"_create_box.html command.
This command only has an effect and is only of use if LAMMPS was
built with the "user-openmp" package included. See the "Making
LAMMPS"_Section_start.html#2_3 section for more info.
[Related commands:]
"processors"_processors.html
[Default:]
nthreads * :pre
or in case multi-threading support is not compiled in:
nthreads 1 :pre
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