python - Enumerating cycles in very large directed graph -

i having trouble finding efficient solution (or solution matter of fact) enumerating cycles in large graph.

the graph has 1 million nodes , 1.25 million edges. have tried using algorithm networkx library, process killed exit code 137 (python) after 24 hours.

i have tried using tarjan's algorithm described here, process has been running 25 days on server, no results yet.

are there approaches recommend find cycles? using mapreduce help? there other approaches large graphs?