Comment (by Roland Haas):

This turns out to be due to these lines

if (local_component != -1) {
  ostringstream buf;
  buf << (vdd.at(Carpet::map)
              ->local_boxes.at(mglevel)
              .at(refinementlevel)
              .at(local_component)
              .active);
  active = buf.str();
}

which are incorrect for arrays whose grid structure is not represented by vdd (which describes only grid functions). This is griggered in Vaishak’s parameter file due to asking for out_vars output of a grid array, in a multi-rank job using Llama. Namely the triggering rank (rank 1 when I tested the parfile) does not own a grid function component on map 0 so the at(local_component) fails (rather than just returning the incorrect string).

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2473/out_vars-incorrectly-uses-grid-fucntion