  In this work, we compare gyrokinetic simulations in stellarators using
different computational domains, namely, flux tube, full-flux-surface, and
radially global domains. Two problems are studied: the linear relaxation of
zonal flows and the linear stability of ion temperature gradient (ITG) modes.
Simulations are carried out with the codes EUTERPE, GENE, GENE-3D, and stella
in magnetic configurations of LHD and W7-X using adiabatic electrons. The zonal
flow relaxation properties obtained in different flux tubes are found to differ
with each other and with the radially global result, except for sufficiently
long flux tubes, in general. The flux tube length required for convergence is
configuration-dependent. Similarly, for ITG instabilities, different flux tubes
provide different results, but the discrepancy between them diminishes with
increasing flux tube length. Full-flux-surface and flux tube simulations show
good agreement in the calculation of the growth rate and frequency of the most
unstable modes in LHD, while for W7-X differences in the growth rates are found
between the flux tube and the full-flux-surface domains. Radially global
simulations provide results close to the full-flux-surface ones. The radial
scale of unstable ITG modes is studied in global and flux tube simulations
finding that in W7-X, the radial scale of the most unstable modes depends on
the binormal wavenumber, while in LHD no clear dependency is found.
