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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>
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<H3>compute sum command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>compute ID group-ID sum compute-ID1 compute-ID2 ...
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
<LI>sum/ = style name of this compute command
<LI>compute-ID1, 2, ... = IDs of computes that calculate per-atom quantities
</UL>
<P><B>Examples:</B>
</P>
<PRE>compute 1 all sum c_force
compute 1 all sum atomKE atomEpair atomEbond
</PRE>
<P><B>Description:</B>
</P>
<P>Define a computation that sums the results of one or more per-atom
computes across all atoms in the group to yield a global scalar or
vector quantity. For example, the forces on a group of atoms could be
summed to yield a net force on the group. The resulting value(s) can
be accessed by any command that uses global computes, e.g. the <A HREF = "therml_style.html">thermo
custom</A> command or <A HREF = "fix_ave_time.html">fix ave/time</A>
command or by a <A HREF = "variable.html">variable</A> command.
</P>
<P>Unlike the "compute sum/atom" command, the result of this is not a
per-atom quantity, but a global scalar or vector. If the other
computes each generate a scalar value per atom, this compute will
generate a single scalar value. If the other computes each generate a
vector of values per atom, this compute will generate a vector of
values. In the latter case, all the other computes must generate
vectors of the same size.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "compute_sum_atom.html">compute sum/atom</A>
</P>
<P><B>Default:</B> none
</P>
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