[SPARK-9975][GraphX] Add Normalized Closeness Centrality to Spark GraphX

[kbastani]

• Added normalized closeness centrality to GraphX library
• Added closeness centrality test suite
• Added closeness centrality operation to GraphOps

Links to JIRA issue: https://issues.apache.org/jira/browse/SPARK-9975

[xdev-developer]

I might be wrong but I think centrality calculation produce wrong results.
Example graph:

Vertices: A, B, C, D, E, F
Edges: (A, B), (A, C), (A, D), (A, E), (A, F)

Calculation result is:

C closeness_centrality: 0.0
B closeness_centrality: 0.0
E closeness_centrality: 0.0
A closeness_centrality: 1.2
F closeness_centrality: 0.0
D closeness_centrality: 0.0

result of A closeness_centrality should be 1.0

[andrewor14]

ok to test. @kbastani can you address the comments? Also maybe this is of interest to @ankurdave.

[SparkQA]

Test build #47750 has finished for PR 8195 at commit 3e900b1.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[skonto]

i will have a look at this.

[srowen]

I doubt this will be merged at this stage given lack of graphx activity. Instead I think this should be closed