1.1 - 8.10 - Modularity Troubleshooting - Teradata Vantage

Teradata Vantage™ - Machine Learning Engine Analytic Function Reference

Product
Teradata Vantage
Release Number
1.1
8.10
Release Date
October 2019
Content Type
Programming Reference
Publication ID
B700-4003-079K
Language
English (United States)

Problem: Function runs slowly for large graphs or terminates unsuccessfully.

If the function terminates unsuccessfully, it displays a failure message.

Workarounds:

  • Consult the logs for error message details and troubleshooting.
  • The logs can help determine the time taken for each iteration. If you know the number of iterations that the function takes (usually 25-50), you can estimate the total execution time.
  • All graph functions operate much faster on INTEGER and BIGINT single-column vertex ids. To create an INTEGER vertex based graph, see Modularity Tips.
  • Compute the modularity in incremental steps by choosing a subset of nodes using the Sources syntax element.
  • If you know some groupings in the graph, specify them with the CommunityAssociation syntax element.
  • If you specified the CommunityEdgeTable syntax element, the reason for slowness might be that the function is writing the community table to the database through JDBC. Run the function without the CommunityEdgeTable syntax element first, to obtain the modularity of the resultant graph.

Problem: Function terminates with errors on Vertices table or Edges table.

Workarounds:

  • Consult the logs for error message details and troubleshooting.
  • Verify that all source and target Vertices in the Edges table are listed in the Vertices table.
  • Verify that the columns representing source and target vertices are not NULL.

Problem: Function completes successfully but results are poor.

Results do not show good modularity or community detection.

Workarounds:

  • Change the value of seed.
  • Multiply the edge weights by a constant.
  • Change the values in the Resolution syntax element.
  • If you know some groupings in the graph, specify them with the CommunityAssociation syntax element.

A poor modularity score can indicate that the graph has no inherent community structure.