  The transformation of cold neutral intergalactic hydrogen into a highly
ionized warm plasma marks the end of the cosmic dark ages and the beginning of
the age of galaxies. The details of this process reflect the nature of the
early sources of radiation and heat, the statistical characteristics of the
large-scale structure of the Universe, the thermodynamics and chemistry of
cosmic baryons, and the histories of star formation and black hole accretion. A
number of massive data sets from new ground- and space-based instruments and
facilities over the next decade are poised to revolutionize our understanding
of primeval galaxies, the reionization photon budget, the physics of the
intergalactic medium (IGM), and the fine-grained properties of hydrogen gas in
the "cosmic web". In this review we survey the physics and key aspects of
reionization-era modeling and describe the diverse range of computational
techniques and tools currently available in this field.
