  For the recent GW100 test set of molecular ionization energies, we present a
comprehensive assessment of different GW methodologies: fully self-consistent
GW (scGW), quasiparticle self-consistent GW (qsGW), partially self-consistent
GW0 (scGW0), perturbative GW (G0W0) and optimized G0W0 based on the
minimization of the deviation from the straight-line error (DSLE-minimized GW).
We compare our GW calculations to coupled-cluster singles, doubles, and
perturbative triples [CCSD(T)] reference data for GW100. We find scGW and qsGW
ionization energies in excellent agreement with CCSD(T), with discrepancies
typically smaller than 0.3 eV (scGW) respectively 0.2 eV (qsGW). For scGW0 and
G0W0 the deviation from CCSD(T) is strongly dependent on the starting point. We
further relate the discrepancy between the GW ionization energies and CCSD(T)
to the deviation from straight line error (DSLE). In DSLE-minimized GW
calculations, the DSLE is significantly reduced, yielding a systematic
improvement in the description of the ionization energies.
