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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>
</CENTER>
<HR>
<H3>next command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>next variables
</PRE>
<UL><LI>variables = one or more variable names
</UL>
<P><B>Examples:</B>
</P>
<PRE>next x
next a t x myTemp
</PRE>
<P><B>Description:</B>
</P>
<P>This command is used with variables defined by the
<A HREF = "variable.html">variable</A> command. It assigns the next value to the
variable from the list of values defined for that variable by the
<A HREF = "variable.html">variable</A> command. Thus when that variable is
subsequently substituted for in an input script command, the new value
is used.
</P>
<P>See the <A HREF = "variable.html">variable</A> command for info on how to define and
use different kinds of variables in LAMMPS input scripts. If a
variable name is a single lower-case character from "a" to "z", it can
be used in an input script command as $a or $z. If it is multiple
letters, it can be used as ${myTemp}.
</P>
<P>If multiple variables are used as arguments to the <I>next</I> command,
then all must be of the same variable style: <I>index</I>, <I>loop</I>,
<I>universe</I>, or <I>uloop</I>. An exception is that <I>universe</I>- and
<I>uloop</I>-style variables can be mixed in the same <I>next</I> command.
<I>Atom</I>- or <I>equal</I>- or <I>world</I>-style variables cannot be incremented
by a next command. All the variables specified are incremented by one
value from their respective lists.
</P>
<P>When any of the variables in the next command has no more values, a
flag is set that causes the input script to skip the next
<A HREF = "jump.html">jump</A> command encountered. This enables a loop containing
a next command to exit.
</P>
<P>When the next command is used with <I>index</I>- or <I>loop</I>-style variables,
the next value is assigned to the variable for all processors. When
the next command is used with <I>universe</I>- or <I>uloop</I>-style variables,
the next value is assigned to whichever processor partition executes
the command first. All processors in the partition are assigned the
same value. Running LAMMPS on multiple partitions of processors via
the "-partition" command-line switch is described in <A HREF = "Section_start.html#2_6">this
section</A> of the manual. <I>Universe</I>- and
<I>uloop</I>-style variables are incremented using the files
"tmp.lammps.variable" and "tmp.lammps.variable.lock" which you will
see in your directory during such a LAMMPS run.
</P>
<P>Here is an example of running a series of simulations using the next
command with an <I>index</I>-style variable. If this input script is named
in.polymer, 8 simulations would be run using data files from
directories run1 thru run8.
</P>
<PRE>variable d index run1 run2 run3 run4 run5 run6 run7 run8
shell cd $d
read_data data.polymer
run 10000
shell cd ..
clear
next d
jump in.polymer
</PRE>
<P>If the variable "d" were of style <I>universe</I>, and the same in.polymer
input script were run on 3 partitions of processors, then the first 3
simulations would begin, one on each set of processors. Whichever
partition finished first, it would assign variable "d" the 4th value
and run another simulation, and so forth until all 8 simulations were
finished.
</P>
<P>Jump and next commands can also be nested to enable multi-level loops.
For example, this script will run 15 simulations in a double loop.
</P>
<PRE>variable i loop 3
variable j loop 5
clear
...
read_data data.polymer.$i$j
print Running simulation $i.$j
run 10000
next j
jump in.script
next i
jump in.script
</PRE>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "jump.html">jump</A>, <A HREF = "include.html">include</A>, <A HREF = "shell.html">shell</A>,
<A HREF = "variable.html">variable</A>,
</P>
<P><B>Default:</B> none
</P>
</HTML>

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