The Loops job identifies cycles of loops inside of the web graph. This is
then used in the LinkRank program to remove those links from consideration
during link analysis.
This job will identify both reciprocal links and cycles of 2+ links up to a
set depth to check. The Loops job is expensive in both computational and
space terms. Because it checks outlinks of outlinks of outlinks for cycles
its intermediate output can be extremly large even if the end output is
rather small. Because of this the Loops job is optional and if it doesn't
exist then it won't be factored into the LinkRank program.