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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@4086 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp 2010-05-05 20:19:26 +00:00
parent 11b28d8711
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2 changed files with 24 additions and 14 deletions
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19
doc/variable.html
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@ -519,9 +519,9 @@ after or in between runs, e.g. by including them in a
<A HREF = "print.html">print</A> command. In this case, if a compute is needed to
evaluate a variable (either directly or indirectly), LAMMPS will not
invoke the compute, but it will use a value previously calculated by
the compute if it is current. Fixes will always provide a quantity
needed by a variable, but the quantity may or may not be current.
This leads to one of three kinds of behavior:
the compute, and can do this only if it is current. Fixes will always
provide a quantity needed by a variable, but the quantity may or may
not be current. This leads to one of three kinds of behavior:
</P>
<P>(1) The variable may be evaluated accurately. If it contains
references to a compute or fix, and these values were calculated on
@ -530,9 +530,11 @@ used by the variable and the result will be accurate.
</P>
<P>(2) LAMMPS may not be able to evaluate the variable and generate an
error. For example, if the variable requires a quantity from a
<A HREF = "compute.html">compute</A> that is not current, LAMMPS will not do it.
This means, for example, that such a variable cannot be evaluated
before the first run has occurred.
<A HREF = "compute.html">compute</A> that is not current, LAMMPS will generate an
error. This means, for example, that such a variable cannot be
evaluated before the first run has occurred. Likewise, in between
runs, such a variable cannot be accessed unless it was evaluated on
the last timestep of the preceding run, e.g. by thermodynamic output.
</P>
<P>One way to get around this problem is to perform a 0-timestep run
before using the variable. For example, these commands
@ -560,7 +562,10 @@ does not change the input state for the 1000-timestep run that
follows. Also note that the 0-timestep run must actually use and
invoke the compute in question (e.g. via <A HREF = "thermo_style.html">thermo</A> or
<A HREF = "dump.html">dump</A> output) in order for it to enable the compute to be
used in a variable after the run.
used in a variable after the run. Thus if you are trying to print a
variable that uses a compute you have defined, you could insure it was
invoked on the last timestep of the preceding run by including it in
thermodynamic output.
</P>
<P>Unlike computes, <A HREF = "fix.html">fixes</A> will never generate an error if
their values are accessed by a variable in between runs. They always

19
doc/variable.txt
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@ -508,9 +508,9 @@ after or in between runs, e.g. by including them in a
"print"_print.html command. In this case, if a compute is needed to
evaluate a variable (either directly or indirectly), LAMMPS will not
invoke the compute, but it will use a value previously calculated by
the compute if it is current. Fixes will always provide a quantity
needed by a variable, but the quantity may or may not be current.
This leads to one of three kinds of behavior:
the compute, and can do this only if it is current. Fixes will always
provide a quantity needed by a variable, but the quantity may or may
not be current. This leads to one of three kinds of behavior:
(1) The variable may be evaluated accurately. If it contains
references to a compute or fix, and these values were calculated on
@ -519,9 +519,11 @@ used by the variable and the result will be accurate.
(2) LAMMPS may not be able to evaluate the variable and generate an
error. For example, if the variable requires a quantity from a
"compute"_compute.html that is not current, LAMMPS will not do it.
This means, for example, that such a variable cannot be evaluated
before the first run has occurred.
"compute"_compute.html that is not current, LAMMPS will generate an
error. This means, for example, that such a variable cannot be
evaluated before the first run has occurred. Likewise, in between
runs, such a variable cannot be accessed unless it was evaluated on
the last timestep of the preceding run, e.g. by thermodynamic output.
One way to get around this problem is to perform a 0-timestep run
before using the variable. For example, these commands
@ -549,7 +551,10 @@ does not change the input state for the 1000-timestep run that
follows. Also note that the 0-timestep run must actually use and
invoke the compute in question (e.g. via "thermo"_thermo_style.html or
"dump"_dump.html output) in order for it to enable the compute to be
used in a variable after the run.
used in a variable after the run. Thus if you are trying to print a
variable that uses a compute you have defined, you could insure it was
invoked on the last timestep of the preceding run by including it in
thermodynamic output.
Unlike computes, "fixes"_fix.html will never generate an error if
their values are accessed by a variable in between runs. They always