Comparison networks differ from RAM’s
in two important aspects. First, they can only perform
comparisons. Second, unlike the RAM model in which
operations occur serially, that is, one after another,
operations in a comparison network may occur the same
time or “in parallel”.
A sorting network is a comparison network for which
the output sequence is monotonically increasing (that is,
b1 b2… bn) for every input sequence (Thomas et al.,
2003).