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doc/compute_property_local.html

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<HTML>

<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>compute property/local command 

</H3>

<P><B>Syntax:</B>

</P>

<PRE>compute ID group-ID property/local input1 input2 ... 

</PRE>

<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command 



<LI>property/local = style name of this compute command 



<LI>input = one or more attributes 



<PRE>  possible attributes = batom1 batom2 btype

                        aatom1 aatom2 aatom3 atype

                        datom1 datom2 datom3 dtype

                        iatom1 iatom2 iatom3 itype 

</PRE>

<PRE>     batom1, batom2 = IDs of 2 atoms in each bond

     btype = bond type of each bond

     aatom1, aatom2, aatom3 = IDs of 3 atoms in each angle

     atype = angle type of each angle

     datom1, datom2, datom3, datom4 = IDs of 4 atoms in each dihedral

     dtype = dihedral type of each dihedral

     iatom1, iatom2, iatom3, iatom4 = IDs of 4 atoms in each improper

     itype = improper type of each improper 

</PRE>



</UL>

<P><B>Examples:</B>

</P>

<PRE>compute 1 all property/local btype batom1 batom2

compute 1 all property/local atype aatom2 

</PRE>

<P><B>Description:</B>

</P>

<P>Define a computation that simply stores the specified attributes as

local vectors or as columns of a local array.  See the

<A HREF = "compute.html">compute</A> command for a discussion of what local

quantities mean, and how they differ from per-atom quantities.  Thus

if the input attributes are for bond information, the local vector or

array that is generated, when aggregated across all processors, will

contain information about all bonds in the system.

</P>

<P>If multiple input attributes are specified then they must all generate

the same amount of information, so that the resulting local array has

the same number of rows for each column.  This means that only bond

attributes can be specified together, or angle attributes, etc.  Bond

and angle attributes can not be mixed in the same compute

property/local command.

</P>

<P>The local data is generated by looping over all the atoms owned on a

processor and extracting bond, angle, etc info.  For bonds, info about

an individual bond will only be included if both atoms in the bond are

in the specified compute group.  Likewise for angles, dihedrals, etc.

</P>

<P>Note that as atoms migrate from processor to processor, there will be

no consistent ordering of the entries within the local vector or array

from one timestep to the next.  The only consistency that is

guaranteed is that the ordering on a particular timestep will be the

same for local info generated by other compute commands.  For example,

output from the <A HREF = "compute_bond_local.html">compute bond/local</A> command

can be combined with bond atom indices from this command and output by

the <A HREF = "dump.html">dump local</A> command in a consistent way.

</P>

<P>The <I>batom1</I> and <I>batom2</I> attributes refer the atom IDs of the 2 atoms

in each <A HREF = "bond_style.html">bond</A>.  The <I>btype</I> attribute refers to the

type of the bond, from 1 to Nbtypes = # of bond types.  The number of

bond types is defined in the data file read by the

<A HREF = "read_data.html">read_data</A> command.  The attributes that start with

"a", "d", "i", refer to similar values for <A HREF = "angle_style.html">angles</A>,

<A HREF = "dihedral_style.html">dihedrals</A>, and <A HREF = "improper_style.html">impropers</A>.

</P>

<P><B>Output info:</B>

</P>

<P>This compute calculates a local vector or local array depending on the

number of input values.  If a single input is specified, a local

vector is produced.  If two or more inputs are specified, a local

array is produced where the number of columns = the number of inputs.

The vector or array can be accessed by any command that uses local

values from a compute as input.  See <A HREF = "Section_howto.html#4_15">this

section</A> for an overview of LAMMPS output

options.

</P>

<P><B>Restrictions:</B> none

</P>

<P><B>Related commands:</B>

</P>

<P><A HREF = "dump.html">dump local</A>, <A HREF = "compute_reduce.html">compute reduce</A>

</P>

<P><B>Default:</B> none

</P>

</HTML>

doc/compute_property_local.txt

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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c



:link(lws,http://lammps.sandia.gov)

:link(ld,Manual.html)

:link(lc,Section_commands.html#comm)



:line



compute property/local command :h3



[Syntax:]



compute ID group-ID property/local input1 input2 ... :pre



ID, group-ID are documented in "compute"_compute.html command :ulb,l

property/local = style name of this compute command :l

input = one or more attributes :l

  possible attributes = batom1 batom2 btype

                        aatom1 aatom2 aatom3 atype

                        datom1 datom2 datom3 dtype

                        iatom1 iatom2 iatom3 itype :pre



     batom1, batom2 = IDs of 2 atoms in each bond

     btype = bond type of each bond

     aatom1, aatom2, aatom3 = IDs of 3 atoms in each angle

     atype = angle type of each angle

     datom1, datom2, datom3, datom4 = IDs of 4 atoms in each dihedral

     dtype = dihedral type of each dihedral

     iatom1, iatom2, iatom3, iatom4 = IDs of 4 atoms in each improper

     itype = improper type of each improper :pre

:ule



[Examples:]



compute 1 all property/local btype batom1 batom2

compute 1 all property/local atype aatom2 :pre



[Description:]



Define a computation that simply stores the specified attributes as

local vectors or as columns of a local array.  See the

"compute"_compute.html command for a discussion of what local

quantities mean, and how they differ from per-atom quantities.  Thus

if the input attributes are for bond information, the local vector or

array that is generated, when aggregated across all processors, will

contain information about all bonds in the system.



If multiple input attributes are specified then they must all generate

the same amount of information, so that the resulting local array has

the same number of rows for each column.  This means that only bond

attributes can be specified together, or angle attributes, etc.  Bond

and angle attributes can not be mixed in the same compute

property/local command.



The local data is generated by looping over all the atoms owned on a

processor and extracting bond, angle, etc info.  For bonds, info about

an individual bond will only be included if both atoms in the bond are

in the specified compute group.  Likewise for angles, dihedrals, etc.



Note that as atoms migrate from processor to processor, there will be

no consistent ordering of the entries within the local vector or array

from one timestep to the next.  The only consistency that is

guaranteed is that the ordering on a particular timestep will be the

same for local info generated by other compute commands.  For example,

output from the "compute bond/local"_compute_bond_local.html command

can be combined with bond atom indices from this command and output by

the "dump local"_dump.html command in a consistent way.



The {batom1} and {batom2} attributes refer the atom IDs of the 2 atoms

in each "bond"_bond_style.html.  The {btype} attribute refers to the

type of the bond, from 1 to Nbtypes = # of bond types.  The number of

bond types is defined in the data file read by the

"read_data"_read_data.html command.  The attributes that start with

"a", "d", "i", refer to similar values for "angles"_angle_style.html,

"dihedrals"_dihedral_style.html, and "impropers"_improper_style.html.



[Output info:]



This compute calculates a local vector or local array depending on the

number of input values.  If a single input is specified, a local

vector is produced.  If two or more inputs are specified, a local

array is produced where the number of columns = the number of inputs.

The vector or array can be accessed by any command that uses local

values from a compute as input.  See "this

section"_Section_howto.html#4_15 for an overview of LAMMPS output

options.



[Restrictions:] none



[Related commands:]



"dump local"_dump.html, "compute reduce"_compute_reduce.html



[Default:] none

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