  We present SoFiA 2, the fully automated 3D source finding pipeline for the
WALLABY extragalactic HI survey with the Australian SKA Pathfinder (ASKAP).
SoFiA 2 is a reimplementation of parts of the original SoFiA pipeline in the C
programming language and makes use of OpenMP for multi-threading of the most
time-critical algorithms. In addition, we have developed a parallel framework
called SoFiA-X that allows the processing of large data cubes to be split
across multiple computing nodes. As a result of these efforts, SoFiA 2 is
substantially faster and comes with a much reduced memory footprint compared to
its predecessor, thus allowing the large WALLABY data volumes of hundreds of
gigabytes of imaging data per epoch to be processed in real-time. The source
code has been made publicly available to the entire community under an
open-source licence. Performance tests using mock galaxies injected into
genuine ASKAP data suggest that in the absence of significant imaging artefacts
SoFiA 2 is capable of achieving near-100% completeness and reliability above an
integrated signal-to-noise ratio of about 5-6. We also demonstrate that SoFiA 2
generally recovers the location, integrated flux and w20 line width of galaxies
with high accuracy. Other parameters, including the peak flux density and w50
line width, are more strongly biased due to the influence of the noise on the
measurement. In addition, very faint galaxies below an integrated
signal-to-noise ratio of about 10 may get broken up into multiple components,
thus requiring a strategy to identify fragmented sources and ensure that they
do not affect the integrity of any scientific analysis based on the SoFiA 2
output.
