GSoC 2024: Betweenness Centrality: Week 6

[bedupako12mas]

Changes to be done in this pull request:

• change betweenness_centrality to centrality
• change the name of docs from pgr_centrality.rst to pgr_betweennessCentrality.rst
• Fix the code for directed graphs
• change betweenesscentrality to betweennessCentrality
• Finish the docs and pgr_betweennessCentrality to experimental.rst
  • could not fix the display query in this PR but it is the first commit in the next one
• finish docqueries
  • cleanup test.conf
  • write explicit, and implicit test cases for directed and undirected graphs
  • for all docqueries test provide by-hand calculation

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Currently I have been using the BGL provided relative betweenness centrality helper function defined in boost/graph/betweenness_centrality.hpp to calculate it. But in its implementation it does not adjust the normalization factor for directed graphs and uses the same factor as the undirected case giving incorrect results. I have fixed this issue by just dividing the result from the helper function by 2.0 in the case for directed graphs hence accounting for the discrepancy.

Normalization factors for directed and undirected graphs:

Implementation for relative betweenness centrality fucntion:

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Manual calculation for docqueries (pgRouting sample data):
edge id < 2 and edge id < 3

edge id < 4 and edge id < 5