ICODE-ADC/lammps
4
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Merge branch 'add-error-explanations' of github.com:akohlmey/lammps into add-error-explanations

Browse Source
This commit is contained in:
Axel Kohlmeyer
2025-02-17 23:06:44 -05:00
parent 841e459b67 25774943d5
commit 1c1749b6bf
1 changed files with 42 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
doc/src/Errors_details.rst
View File

@ -420,6 +420,48 @@ different arguments.
This error message might also require a close look at other LAMMPS input files This error message might also require a close look at other LAMMPS input files
that are read in by the input script, such as data files or restart files. that are read in by the input script, such as data files or restart files.
.. _err0021:
Energy was not tallied on needed timestep (also virial, per-atom energy, per-atom virial)
-----------------------------------------------------------------------------------------
This error is generated when LAMMPS attempts to access an out-of-date
or non-existent energy, pressure, or virial.
For efficiency reasons,
LAMMPS does *not* calculate these quantities when the forces are calculated
on every timestep or iteration. Global quantities are only calculated
when they are needed for :doc:`thermo <thermo_style>` output (at the beginning, end,
and at regular intervals specified by the :doc:`thermo <thermo>` command). Similarly,
per-atom quantities are only calculated if they are needed to write per-atom
energy or virial to a dump file.
This system works fine for simple input scripts.
However, the many user-specified `variable`, `fix`, and `compute` commands
that LAMMPS provides make it difficult to anticipate when a quantity will
be requested. In some use cases, LAMMPS will figure out that a quantity is needed
and arrange for it to be calculated on that timestep e.g. if it is requested by
:doc:`fix ave/time <fix_ave_time>` or similar commands.
If that fails, it can be detected by a mismatch
between the current timestep and when a quantity was last calculated,
in which case an error message of this type is generated.
The most common cause of this type of error is requesting a quantity before
the start of the simulation.
.. code-block:: LAMMPS
# run 0 post no # this will fix the error
variable e equal pe # requesting energy compute
print "Potential energy = $e" # this will generate the error
run 1000 # start of simulation
This situation can be avoided by adding in a "run 0" command, as explained in
more detail in the "Variable Accuracy" section of the
:doc:`variable <variable>` doc page.
Another cause is requesting a quantity on a timestep that is not
a thermo or dump output timestep. This can often be
remedied by increasing the frequency of thermo or dump output.
.. _err0024: .. _err0024:
Molecule topology/atom exceeds system topology/atom Molecule topology/atom exceeds system topology/atom