On the use of semi-numerical simulations in predicting the 21-cm signal
  from the epoch of reionization
  We present a detailed comparison of three different simulations of the epoch
of reionization (EoR). The radiative transfer simulation (${\rm C}^2$-RAY)
among them is our benchmark. Radiative transfer codes can produce realistic
results, but are computationally expensive. We compare it with two
semi-numerical techniques: one using the same halos as ${\rm C}^2$-RAY as its
sources (Sem-Num), and one using a conditional Press-Schechter scheme (CPS+GS).
These are vastly more computationally efficient than ${\rm C}^2$-RAY, but use
more simplistic physical assumptions. We evaluate these simulations in terms of
their ability to reproduce the history and morphology of reionization. We find
that both Sem-Num and CPS+GS can produce an ionization history and morphology
that is very close to ${\rm C}^2$-RAY, with Sem-Num performing slightly better
compared to CPS+GS.
  We also study different redshift space observables of the 21-cm signal from
EoR: the variance, power spectrum and its various angular multipole moments. We
find that both semi-numerical models perform reasonably well in predicting
these observables at length scales relevant for present and future experiments.
However, Sem-Num performs slightly better than CPS+GS in producing the
reionization history, which is necessary for interpreting the future
observations.
