forked from lijiext/lammps
137 lines
4.4 KiB
HTML
137 lines
4.4 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>jump command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>jump file label
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</PRE>
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<UL><LI>file = filename of new input script to switch to
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<LI>label = optional label within file to jump to
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>jump newfile
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jump in.run2 runloop
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jump SELF runloop
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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 closes the current input script file, opens the file with
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the specified name, and begins reading LAMMPS commands from that file.
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Unlike the <A HREF = "include.html">include</A> command, the original file is not
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returned to, although by using multiple jump commands it is possible
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to chain from file to file or back to the original file.
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</P>
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<P>If the word "SELF" is used for the filename, then the current input
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script is re-opened and read again.
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</P>
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<P>IMPORTANT NOTE: The SELF option is not guaranteed to work when the
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current input script is being read through stdin (standard input),
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e.g.
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</P>
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<PRE>lmp_g++ < in.script
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</PRE>
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<P>since the SELF option invokes the C-library rewind() call, which may
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not be supported for stdin on some systems or by some MPI
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implementations. This can be worked around by using the <A HREF = "Section_start.html#start_7">-in
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command-line argument</A>, e.g.
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</P>
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<PRE>lmp_g++ -in in.script
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</PRE>
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<P>or by using the <A HREF = "Section_start.html#start_7">-var command-line
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argument</A> to pass the script name as a
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variable to the input script. In the latter case, a
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<A HREF = "variable.html">variable</A> called "fname" could be used in place of
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SELF, e.g.
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</P>
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<PRE>lmp_g++ -var fname in.script < in.script
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</PRE>
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<P>The 2nd argument to the jump command is optional. If specified, it is
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treated as a label and the new file is scanned (without executing
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commands) until the label is found, and commands are executed from
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that point forward. This can be used to loop over a portion of the
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input script, as in this example. These commands perform 10 runs,
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each of 10000 steps, and create 10 dump files named file.1, file.2,
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etc. The <A HREF = "next.html">next</A> command is used to exit the loop after 10
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iterations. When the "a" variable has been incremented for the tenth
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time, it will cause the next jump command to be skipped.
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</P>
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<PRE>variable a loop 10
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label loop
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dump 1 all atom 100 file.$a
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run 10000
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undump 1
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next a
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jump in.lj loop
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</PRE>
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<P>If the jump <I>file</I> argument is a variable, the jump command can be
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used to cause different processor partitions to run different input
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scripts. In this example, LAMMPS is run on 40 processors, with 4
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partitions of 10 procs each. An in.file containing the example
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variable and jump command will cause each partition to run a different
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simulation.
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</P>
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<PRE>mpirun -np 40 lmp_ibm -partition 4x10 -in in.file
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</PRE>
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<PRE>variable f world script.1 script.2 script.3 script.4
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jump $f
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</PRE>
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<P>Here is an example of a loop which checks every 1000 steps if the
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system temperature has reached a certain value, and if so, breaks out
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of the loop to finish the run. Note that any variable could be
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checked, so long as it is current on the timestep when the run
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completes. As explained on the <A HREF = "variable.html">variable</A> doc page,
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this can be insured by includig the variable in thermodynamic output.
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</P>
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<PRE>variable myTemp equal temp
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label loop
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variable a loop 1000
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run 1000
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if "${myTemp} < 300.0" then "jump SELF break"
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next a
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jump SELF loop
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label break
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print "ALL DONE"
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</PRE>
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<P>Here is an example of a double loop which uses the if 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 SELF 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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next a
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jump SELF loopa
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</PRE>
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<P><B>Restrictions:</B>
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</P>
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<P>If you jump to a file and it does not contain the specified label,
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LAMMPS will come to the end of the file and exit.
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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 = "variable.html">variable</A>, <A HREF = "include.html">include</A>, <A HREF = "label.html">label</A>,
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<A HREF = "next.html">next</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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