[GraphHopper] Question on PrepareContractionHierarchies

[Renaud De Landtsheer]

Dear Peter,

I have a question on the PrepareContractionHierarchies algo.

There is a class LevelEdgeFilterCH, which is used in the Dijkstra to 
check if the shortest path between two non-contracted nodes pass through 
a node that we want to contract.

My point is that this class inherits from LevelEdgeFilter, and uses its 
check,
and I do not understand why; I fear that there is something I do not 
understand.

LevelEdgeFilter prevents us from strictly going down in the hierarchy.
and LevelEdgeFilterCH check this condition first.
If it is OK, it further check that the neighbour node is not contracted, 
that is: of level zero.
Knowing that the source node is also non-contracted, this second check 
seems stronger than the first check inherited from the LevelEdgeFilter 
class.

Thank you for your help.

-- 
*Renaud De Landtsheer, Ir, Phd*
Sr R&D Engineer
CETIC
Rue des Frères Wright, 29/3
B-6041 Charleroi
Phone: +32 71 490 754


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