forked from lijiext/lammps
64 lines
1.9 KiB
Plaintext
64 lines
1.9 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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processors command :h3
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[Syntax:]
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processors Px Py Pz :pre
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Px,Py,Pz = # of processors in each dimension of a 3d grid :ul
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[Examples:]
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processors 2 4 4
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processors * * 5
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processors * 1 10 :pre
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[Description:]
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Specify how processors are mapped as a 3d logical grid to the global
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simulation box, namely Px by Py by Pz.
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Any of the Px, Py, Pz parameters can be specified with an asterisk
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"*", which means LAMMPS will choose the number of processors in that
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dimension. It will do this based on the size and shape of the global
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simulation box so as to minimize the surface-to-volume ratio of each
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processor's sub-domain.
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Since LAMMPS does not load-balance by changing the grid of 3d
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processors on-the-fly, this command can be used to override the LAMMPS
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default if it is known to be sub-optimal for a particular problem.
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For example, a problem where the atom's extent will change
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dramatically in a particular dimension over the course of the
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simulation.
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The product of Px, Py, Pz must equal P, the total # of processors
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LAMMPS is running on. For a "2d simulation"_dimension.html, Pz must
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equal 1. If multiple partitions are being used then P is the number
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of processors in this partition; see "this
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section"_Section_start.html#2_6 for an explanation of the -partition
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command-line switch.
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Note that if you run on a large, prime number of processors P, then a
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grid such as 1 x P x 1 will be required, which may incur extra
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communication costs.
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[Restrictions:]
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This command cannot be used after the simulation box is defined by a
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"read_data"_read_data.html or "create_box"_create_box.html command.
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It can be used before a restart file is read to change the 3d
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processor grid from what is specified in the restart file.
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[Related commands:] none
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[Default:]
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Px Py Pz = * * *
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