# pathfinding: capacity-dependent apriori model probability (path finding)

https://github.com/lightningnetwork/lnd/pull/6857

Host: bitromortac -

## Notes

- In this PR review club we will have a closer look at pathfinding internals and
upcoming improvements in this regard.
- Original issue: https://github.com/lightningnetwork/lnd/issues/5988
- Follow-up PR: https://github.com/lightningnetwork/lnd/pull/6815

- Additional info:
- https://en.wikipedia.org/wiki/Graph_(discrete_mathematics)
- https://en.wikipedia.org/wiki/Shortest_path_problem

## Questions

- What is the underlying algorithm used for pathfinding, where is it located in the LND code base?
- Whatâ€™s the graph type of the Lightning network in your opinion (in terms of pathfinding)?
- What kind of ingredients enter into the pathfinding edge weight?
- What is the role of the probability term?
- Why should we include the capacity into pathfinding?
- Whatâ€™s the commit adding the new functionality?
- Why donâ€™t we just introduce a hard cutoff say at 3/4 of the channel capacity?
- How is the probability of an edge altered, what is its effect (look at
`TestCapacityCutoff`

)? - Are channel capacities part of the gossip protocol? Are there cases when they are not available?
- Which API endpoints are altered by this change?