Posthoc: The Visualisation Platform for Search

Search, especially pathfinding search, is a foundational problem-solving technique in Computer Science for sequential-decision making problems. Such algorithms appear widely in the academic literature and they have found broad applicability including in personal navigation, robotics and computer games. Despite their importance, search algorithms can be challenging for practitioners to implement and difficult for learners to understand. In this work, we present POSTHOC, a visualisation and debugging tool which aims to improve the situation. Our approach relies on search traces, textual records of key operations that occur during the search process; e.g., node expansion, successor generation and other events of interest. We employ search traces to visualise the decision-making process and to construct domain-specific representations for each event. We show how these traces can be used — in a variety of contexts — to inspect, debug, and better understand search algorithms. Finally, we demonstrate POSTHOC in a range of different real-world case studies.