Error on dump_modify

I was trying to skip dump for the first few timesteps. I tried to use the dump_modify skip command but I am getting an error. Can anyone help me to resolve this?

Syntax used:
dump 1 all custom 1000 dump_lang.lammpstrj id mol type x y z vx vy vz
dump_modify 1 skip v_et < 10000

ERROR: Illegal dump_modify command (src/dump.cpp:1134)
Last command: dump_modify 1 skip v_et < 10000

What about:

dump 1 all custom 1000 dump_lang.lammpstrj id mol type x y z vx vy vz
variable et equal step<10000
dump_modify 1 skip v_et

This still gives me same error without any proper explanation.

ERROR: Illegal dump_modify command (src/dump.cpp:1134)
Last command: dump_modify 1 skip v_et

May be your LAMMPS version is old. I am using 2 Aug 2023, what about you ?

edit: skip was added in version 15Sep2022

I think that might be the reason as I am using the 31 Aug 2021 build. Thank you for pointing that out. Can you guide me on how I can update my Lammps installation without uninstalling it completely?

Is there any other way to get dump from a certain timestep?

Just compile a new version: 2. Install LAMMPS — LAMMPS documentation

1 Like

Thanks for all your help. I got a workaround for this by dividing the run into separate parts and dumping after depositing all the molecules.

Why this may work around the current issue, it may not be easy to find a workaround for any other new feature that you would want to use. Not to mention that you are missing out on all bug fixes in a newer version of LAMMPS. Whan starting a new project is always recommended to start with an up-to-date LAMMPS version. Outside of laziness there is not much of a reason to stick with an old version.