forked from lijiext/lammps
69 lines
2.2 KiB
HTML
69 lines
2.2 KiB
HTML
<HTML>
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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<HR>
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<H3>processors command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>processors Px Py Pz
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</PRE>
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<UL><LI>Px,Py,Pz = # of processors in each dimension of a 3d grid
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>processors 2 4 4
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processors * * 5
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processors * 1 10
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>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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</P>
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<P>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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</P>
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<P>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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</P>
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<P>The product of Px, Py, Pz must equal P, the total # of processors
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LAMMPS is running on. For a <A HREF = "dimension.html">2d simulation</A>, 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 <A HREF = "Section_start.html#start_6">this
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section</A> for an explanation of the
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-partition command-line switch.
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</P>
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<P>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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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>This command cannot be used after the simulation box is defined by a
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<A HREF = "read_data.html">read_data</A> or <A HREF = "create_box.html">create_box</A> 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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</P>
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<P><B>Related commands:</B> none
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</P>
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<P><B>Default:</B>
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</P>
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<P>Px Py Pz = * * *
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</P>
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</HTML>
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