The current rank optimizer yields incorrect values for this input graph:

digraph { "G"->"C" "H"->"C" "C"->"I" "Q"->"G" "W"->"G" "M"->"H" "I"->"04" "Q"->"J" "05"->"J" "R"->"L" "X"->"M" "11"->"Q" "12"->"W" "18"->"03" "19"->"03" "20"->"11" "21"->"12" "10"->"18" "X"->"19" "23"->"19" "25"->"23" "05"->"25" "24"->"21" }

In this graph, both G and H should be in an earlier rank than C. This is reflected correctly in the rank initializer: H=4, G=8, C=10. However, post optimization, H has a later rank than C: G=-2, H=4, C=0.