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<div class="moz-cite-prefix">Hi Renaud,<br>
<br>
the LevelEdgeFilterCH (additionally to the hierarchy filtering)
just makes sure that the specified node is excluded from the
dijkstra. If the dijkstra finds a shorter path (without that node)
we do not need the shortcut. E.g.:<br>
<pre> | |
..-A--B--C
| |
\-D-E-/
</pre>
To contract B we introduce several shortcuts. One of them is the
shortcut from A to C. But we can avoid that if we find a shorter
way from A to C without B.<br>
<br>
Regards,<br>
Peter.<br>
<br>
</div>
<blockquote cite="mid:524BF321.50003@cetic.be" type="cite">
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charset=ISO-8859-1">
Dear Peter, <br>
<br>
I have a question on the PrepareContractionHierarchies algo. <br>
<br>
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. <br>
<br>
My point is that this class inherits from LevelEdgeFilter, and
uses its check, <br>
and I do not understand why; I fear that there is something I do
not understand. <br>
<br>
LevelEdgeFilter prevents us from strictly going down in the
hierarchy. <br>
and LevelEdgeFilterCH check this condition first. <br>
If it is OK, it further check that the neighbour node is not
contracted, that is: of level zero. <br>
Knowing that the source node is also non-contracted, this second
check seems stronger than the first check inherited from the
LevelEdgeFilter class. <br>
<br>
Thank you for your help. <br>
<br>
<div class="moz-signature">-- <br>
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