Comment (by Leonardo Werneck):

Gabriele---

Upon further discussion, the functionality you seek is already provided by the thorn, although it is not its default behavior. For example, the following non-standard output configuration:

particle_tracerET::output_freq   = 4
particle_tracerET::output_format = "ascii" # Default

can be made standard by doing

particle_tracerET::output_freq = 0
<...>
CarpetIOASCII::out1D_every = 128 # Or whatever
CarpetIOASCII::out1D_vars  = "
  <...>
  particle_tracerET::particle_position_arrays{out_every=4}
"

Note that in the standard output the particle positions would be in the file particle_traceret-particle_position_arrays.x.asc, while the non-standard output file is named particles.asc. In fact one can enable both outputs at the same time using e.g.,

particle_tracerET::output_freq = 4
<...>
CarpetIOASCII::out1D_every = 128 # Or whatever
CarpetIOASCII::out1D_vars  = "
  <...>
  particle_tracerET::particle_position_arrays{out_every=particle_tracerET::output_freq}
"

Granted, this is not well documented, so we should add this to the thorn’s documentation.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2691/new-features-to-particle_traceret