forked from lijiext/lammps
136 lines
4.9 KiB
HTML
136 lines
4.9 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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</CENTER>
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<HR>
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<H3>next command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>next variables
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</PRE>
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<UL><LI>variables = one or more variable names
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>next x
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next a t x myTemp
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>This command is used with variables defined by the
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<A HREF = "variable.html">variable</A> command. It assigns the next value to the
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variable from the list of values defined for that variable by the
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<A HREF = "variable.html">variable</A> command. Thus when that variable is
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subsequently substituted for in an input script command, the new value
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is used.
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</P>
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<P>See the <A HREF = "variable.html">variable</A> command for info on how to define and
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use different kinds of variables in LAMMPS input scripts. If a
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variable name is a single lower-case character from "a" to "z", it can
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be used in an input script command as $a or $z. If it is multiple
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letters, it can be used as ${myTemp}.
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</P>
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<P>If multiple variables are used as arguments to the <I>next</I> command,
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then all must be of the same variable style: <I>index</I>, <I>loop</I>, <I>file</I>,
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<I>universe</I>, or <I>uloop</I>. An exception is that <I>universe</I>- and
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<I>uloop</I>-style variables can be mixed in the same <I>next</I> command.
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</P>
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<P>All the variables specified with the next command are incremented by
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one value from their respective list of values. A <I>file</I>-style variable
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reads the next line from its associated file. <I>String-</I> or <I>atom</I>- or
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<I>equal</I>- or <I>world</I>-style variables cannot be used with the the next
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command, since they only store a single value.
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</P>
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<P>When any of the variables in the next command has no more values, a
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flag is set that causes the input script to skip the next
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<A HREF = "jump.html">jump</A> command encountered. This enables a loop containing
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a next command to exit. As explained in the <A HREF = "variable.html">variable</A>
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command, the variable that has exhausted its values is also deleted.
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This allows it to be used and re-defined later in the input script.
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<I>File</I>-style variables are exhausted when the end-of-file is reached.
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</P>
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<P>When the next command is used with <I>index</I>- or <I>loop</I>-style or
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<I>file</I>-style variables, the next value is assigned to the variable for
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all processors. When the next command is used with <I>universe</I>- or
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<I>uloop</I>-style variables, the next value is assigned to whichever
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processor partition executes the command first. All processors in the
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partition are assigned the same value. Running LAMMPS on multiple
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partitions of processors via the "-partition" command-line switch is
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described in <A HREF = "Section_start.html#start_7">this section</A> of the manual.
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<I>Universe</I>- and <I>uloop</I>-style variables are incremented using the
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files "tmp.lammps.variable" and "tmp.lammps.variable.lock" which you
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will see in your directory during such a LAMMPS run.
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</P>
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<P>Here is an example of running a series of simulations using the next
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command with an <I>index</I>-style variable. If this input script is named
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in.polymer, 8 simulations would be run using data files from
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directories run1 thru run8.
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</P>
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<PRE>variable d index run1 run2 run3 run4 run5 run6 run7 run8
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shell cd $d
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read_data data.polymer
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run 10000
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shell cd ..
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clear
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next d
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jump in.polymer
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</PRE>
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<P>If the variable "d" were of style <I>universe</I>, and the same in.polymer
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input script were run on 3 partitions of processors, then the first 3
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simulations would begin, one on each set of processors. Whichever
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partition finished first, it would assign variable "d" the 4th value
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and run another simulation, and so forth until all 8 simulations were
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finished.
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</P>
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<P>Jump and next commands can also be nested to enable multi-level loops.
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For example, this script will run 15 simulations in a double loop.
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</P>
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<PRE>variable i loop 3
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variable j loop 5
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clear
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...
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read_data data.polymer.$i$j
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print Running simulation $i.$j
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run 10000
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next j
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jump in.script
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next i
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jump in.script
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</PRE>
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<P>Here is an example of a double loop which uses the <A HREF = "if.html">if</A> and
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<A HREF = "jump.html">jump</A> commands to break out of the inner loop when a
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condition is met, then continues iterating thru the outer loop.
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</P>
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<PRE>label loopa
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variable a loop 5
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label loopb
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variable b loop 5
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print "A,B = $a,$b"
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run 10000
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if $b > 2 then "jump in.script break"
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next b
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jump in.script loopb
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label break
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variable b delete
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</PRE>
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<PRE>next a
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jump in.script loopa
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</PRE>
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "jump.html">jump</A>, <A HREF = "include.html">include</A>, <A HREF = "shell.html">shell</A>,
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<A HREF = "variable.html">variable</A>,
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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