  In this work, a comparison of the global gyrokinetic codes EUTERPE and
GENE-3D in stellarator configurations of LHD and W7-X is carried out. In linear
simulations with adiabatic electrons, excellent agreement is found in the mode
numbers, growth rate and frequency, mode structure, and spatial localization of
the most unstable mode in LHD. In W7-X, the dependence of the growth rate and
frequency with the mode number is well reproduced by both codes. The codes are
also compared in linear simulations with kinetic ions and electrons in W7-X
using model profiles, and reasonable agreement is found in the wavenumber of
the most unstable modes. A stabilization of small-scale modes in
kinetic-electron simulations with respect to the adiabatic-electron case is
consistently found in both codes. Nonlinear simulations using adiabatic
electrons and model profiles are also studied and the heat fluxes are compared.
Very good agreement is found in the turbulent ion heat fluxes in both LHD and
W7-X. Two problems that cannot be properly accounted for in local flux tube
codes are studied: the localization of instabilities and turbulence over the
flux surface and the influence of a background long-wavelength electric field.
Good agreement between codes is found with respect to the spatial localization
of instabilities and turbulence over the flux surface. The localization of
saturated turbulence is found in both codes to be much smaller than that of the
linear instabilities and smaller than previously reported in full-surface
radially-local simulations. The influence of the electric field on the
localization is also found to be smaller in the developed turbulent state than
in the linear phase, and smaller than in previous works. A stabilizing effect
of a constant electric field on the linearly unstable modes is found in both
codes. A moderate reduction of turbulent transport by the radial electric
field...
