ASF GitHub Bot commented on IGNITE-8059:

Github user asfgit closed the pull request at:


> Integrate decision tree with partition based dataset
> ----------------------------------------------------
>                 Key: IGNITE-8059
>                 URL: https://issues.apache.org/jira/browse/IGNITE-8059
>             Project: Ignite
>          Issue Type: Improvement
>          Components: ml
>            Reporter: Anton Dmitriev
>            Assignee: Anton Dmitriev
>            Priority: Major
>             Fix For: 2.5
> A partition based dataset (new underlying infrastructure component) was added 
> as part of IGNITE-7437 and now we need to adopt decision tree algorithm to 
> work on top of this infrastructure.
> ----
> The way decision tree algorithm is implemented on top of a row-partitioned 
> data is described further.
> At first, the basic idea behind any decision tree, bother regression and 
> classification, is to find the *data split* that allows to minimize an 
> *impurity measure* like [Gini 
> coefficient|https://en.wikipedia.org/wiki/Gini_coefficient], 
> [entropy|https://en.wikipedia.org/wiki/Entropy_(information_theory)] or [mean 
> squared error|https://en.wikipedia.org/wiki/Mean_squared_error]. To calculate 
> the best split we need to build a _function_ that describes dependency 
> between split point (independent variable) and impurity measure (dependent 
> variable) and then find a minimum of this _function_.
> In case of a distributed system, when a data is partitioned by row, we can 
> calculate such _function_ on every node, compress it somehow, and then pass 
> it to the master node. On the master node we need to summarize _functions_ 
> received from all nodes and then find a minimum of the result _function_. 
> It's the way decision tree algorithm is implemented in Apache Ignite ML 
> module.

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