Module ctw 

Context Tree Weighting (CTW) and Factorized Action-Conditional CTW (FAC-CTW).

This module implements both the standard CTW algorithm for binary sequence prediction and the FAC-CTW variant described in Veness et al. (2011) for agent-based prediction.

Arena Allocator

For performance with deep trees (D > 64), nodes are stored in a flat arena using indices rather than Box pointers, eliminating pointer chasing and improving cache locality.

Shared History Optimization (FAC-CTW)

FAC-CTW uses k trees that share the same base history. Rather than duplicating the history k times, a single shared history is maintained with per-tree length tracking.

Structs

ContextTree

A Context Tree for binary sequence prediction using arena allocation.

CtArena

Arena allocator for context tree nodes.

CtNode

A node in the Context Tree, stored in an arena.

FacContextTree

Factorized Action-Conditional Context Tree Weighting.

NodeIndex

Index into the node arena. NONE indicates no child.