Extending the Tsetlin Machine With Integer-Weighted Clauses for
  Increased Interpretability
  Despite significant effort, building models that are both interpretable and
accurate is an unresolved challenge for many pattern recognition problems. In
general, rule-based and linear models lack accuracy, while deep learning
interpretability is based on rough approximations of the underlying inference.
Using a linear combination of conjunctive clauses in propositional logic,
Tsetlin Machines (TMs) have shown competitive performance on diverse
benchmarks. However, to do so, many clauses are needed, which impacts
interpretability. Here, we address the accuracy-interpretability challenge in
machine learning by equipping the TM clauses with integer weights. The
resulting Integer Weighted TM (IWTM) deals with the problem of learning which
clauses are inaccurate and thus must team up to obtain high accuracy as a team
(low weight clauses), and which clauses are sufficiently accurate to operate
more independently (high weight clauses). Since each TM clause is formed
adaptively by a team of Tsetlin Automata, identifying effective weights becomes
a challenging online learning problem. We address this problem by extending
each team of Tsetlin Automata with a stochastic searching on the line (SSL)
automaton. In our novel scheme, the SSL automaton learns the weight of its
clause in interaction with the corresponding Tsetlin Automata team, which, in
turn, adapts the composition of the clause by the adjusting weight. We evaluate
IWTM empirically using five datasets, including a study of interpetability. On
average, IWTM uses 6.5 times fewer literals than the vanilla TM and 120 times
fewer literals than a TM with real-valued weights. Furthermore, in terms of
average F1-Score, IWTM outperforms simple Multi-Layered Artificial Neural
Networks, Decision Trees, Support Vector Machines, K-Nearest Neighbor, Random
Forest, XGBoost, Explainable Boosting Machines, and standard and real-value
weighted TMs.
