Module depth2 

Specialised solvers for trees of depth one and two.

Instead of recursing, they count the classes of every pair of features once, in a matrix, and deduce every leaf of every depth-2 tree from it. DL8.5 uses them for the last two levels, and LGDT uses them at each step. The idea comes from MurTree (Demirović et al., JMLR 2022).

Structs

ErrorMinimizer

Depth-2 solver that minimises the error of the tree: the optimal tree of depth at most 2.

InfoGainMaximizer

Depth-2 solver that maximises the information gain of the tree rather than minimising its error. Used by LGDT for a less greedy lookahead.

Traits

OptimalDepth2Tree

A solver for trees of depth at most 2.