LanX,
Here is an actual example - one that I tested with: 
   L     F       B
 / | \ /  \    / | \
R--J--X----D--Q  P  M
 \ | /         \ |  |
   Z             U--S

[download]

Let's say I am trying to find all paths between D and M. I have intentionally made a left hand side and a right hand side so all paths going to the left of D will be invalid because they will require coming back through D to get to M. Now, let's say I first start descending from D -> X and beyond and unwind back to D in failure. Now I go to D -> F -> X. I already determined that paths to X coming from D are bad so I can stop here.

Regarding your initial idea. That is called a bi-directional search and was my first inclination too assuming only the shortest path(s) were desired. Unfortunately, if there is a 3 node solution and a 7 node solution, neversaint wants both.

Cheers - L~R

In reply to Re^2: Short Circuiting DFS Graph Traversal by Limbic~Region
in thread Short Circuiting DFS Graph Traversal by Limbic~Region

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