The counts are usually not needed during decoding and are not loaded
from the phrase table. This is just a workaround that can make them
available to features which have a use for them.
If you need access to the counts, copy the two marginal counts and the
joint count into an additional information property with key "Counts",
e.g. using awk:
$ zcat phrase-table.gz | awk -F' \|\|\| ' '{printf("%s {{Counts %s}}\n",$0,$5);}' | gzip -c > phrase-table.withCountsPP.gz
CountsPhraseProperty reads them from the phrase table and provides
methods GetSourceMarginal(), GetTargetMarginal(), GetJointCount().
Derive your property class from PhraseProperty. Do any expensive string
processing of the property value in there, not in the feature
implementation, and provide methods to access the information in
appropriate data formats. The property value string will thus have to
be processed only once (on loading) rather than each time the respective
phrase is applied and your feature needs to access the property value.
