gracefully report error in CGPM for latent categoricals without specified number of categories · probcomp/bayeslite#461

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描述

CREATE GENERATOR g FOR p USING cgpm (
    LATENT y CATEGORICAL,
    MODEL y GIVEN x USING whatever,
    MODEL z GIVEN y USING frobnosticator
)

In order to use the latent categorical (or, 'nominal') variable y as an input of the frobnosticator model, CGPM wants to know fictitious distribution parameters, namely the number of categories (or, 'names' or 'labels'), but there is no way to ascertain this because x is latent and does not actually appear in the table. The _default_categorical (or, _default_nominal) method will fail trying to select a nonexistent variable from the table -- or maybe quietly return 1 because of the usual sqlite3 quotation misfeature.

Not tested; observed by code inspection.

Alternative fix: Obviate the need to specify fictitious distribution parameters. This requires changes to CGPM.

貢獻者指南

技術棧: python
領域: backenddata
議題類型: bug
難度: 3
預計時間: 1-3 hours
活動狀態: stale
清晰度: clear
前置要求: Python
新手友善度: 45
研究方向: Look at the default categorical method in the CGPM implementation (likely in cgpm.py). The issue occurs when a latent categorical variable is used as an input without specifying the number of categories. The method tries to fetch a nonexistent column from the table. Add a check for latent variables and raise a clear error message. Alternatively, consider modifying the CGPM to infer the number of categories from the model parameters if possible.