subsection Postprocess
set List of postprocessors = velocity statistics, temperature statistics, visualization, heat flux statistics, depth average, particles, Stokes residual, basic statistics, mobility statistics
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Howevery, once I deleted “particles” in the Postprocess subsection “List of postprocessors”, the two compositions “1_mantle” “3_continent” and their corresponding material properties in the model disappeared. I am wondering whether or not I am missing something here? Why choosing not to output “particles” will affect the calculation?
@xiang This is a historical accident. When we implemented particles first, we implemented it as a “postprocessor”, i.e., something that is run after all of the other computations of the time step were done. As a consequence, if you want particles as part of your simulation, you need to list particles among the postprocessors. If you don’t, no particles will ever be created – you are just setting parameters in the input file that have no consequence because nobody ever reads these parameters.
By the way, this has nothing to do with “output”. Postprocessors do something at the end of a time step, and outputting information could be one of the things they do, but that is not necessary.
However, there is still the option to not output the particles (if you want to save disk space), by either setting in the Postprocess/Particles subsection Time between data output to something very large, or setting Data output format to none, both of which will disable particle output, without disabling the particles (and their information) themselves.