[Mbs_part] Threshold option not taken into account
The user option
mbs_part->options->treshold = 1.0e-10;
is currently not used during mbs_part module. In fact,
mbs_data->NRerr is used per default during mbs_close_geo.
Copying the value wanted by the user for mbs_part with something like this
mbs_data->NRerr = mbs_part->options->treshold;
and then return back to the default value of NRerr.
ps: treshold should be threshold ;)