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https://issues.apache.org/jira/browse/MADLIB-1351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16873498#comment-16873498
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Scott Hajek commented on MADLIB-1351:
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I like the proposed API for stopping criterion on LDA. I think *evaluate_every*
and *perp_tol* are sufficient, and the default values are reasonable. I might
suggest calling the latter by a slightly less abbreviated name for clarity,
like *perplex_tol* or *perplexity_tol*. The brevity isn't as necessary in
MADlib since you don't/can't specify with keyword arguments in SQL function
calls anyway. It's mainly for documentation.
Although I guess [named
notation|[https://www.postgresql.org/docs/9.0/sql-syntax-calling-funcs.html]]
will be (or maybe already is) available once Greenplum catches up with later
versions of Postgres. In that case, maybe a good compromise would be
*perplex_tol*.
> Add stopping criteria on perplexity to LDA
> ------------------------------------------
>
> Key: MADLIB-1351
> URL: https://issues.apache.org/jira/browse/MADLIB-1351
> Project: Apache MADlib
> Issue Type: Improvement
> Components: Module: Parallel Latent Dirichlet Allocation
> Reporter: Frank McQuillan
> Assignee: Himanshu Pandey
> Priority: Minor
> Fix For: v1.17
>
>
> In LDA
> http://madlib.apache.org/docs/latest/group__grp__lda.html
> make stopping criteria on perplexity rather than just number of iterations.
> Suggested approach is to do what scikit-learn does
> https://scikit-learn.org/stable/modules/generated/sklearn.decomposition.LatentDirichletAllocation.html
> evaluate_every : int, optional (default=0)
> How often to evaluate perplexity. Set it to 0 or negative number to not
> evaluate perplexity in training at all. Evaluating perplexity can help you
> check convergence in training process, but it will also increase total
> training time. Evaluating perplexity in every iteration might increase
> training time up to two-fold.
> perp_tol : float, optional (default=1e-1)
> Perplexity tolerance in batch learning. Only used when evaluate_every is
> greater than 0.
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