A Time-Based Intra-Memory Computing Graph Processor Featuring A* Wavefront Expansion and 2-D Gradient Control

A mixed-signal, time-based 65-nm application-specific integrated circuit is developed for solving shortest-path problems. Digital circuits are collocated with the memory as intra-memory computing. The core follows similar principles from wave routing and, additionally, incorporates a gradient on the periphery of the core to implement the A* algorithm predicted distance heuristic. A leading pulse is propagated from start nodes and is asynchronously latched in neighboring vertex cells and pushed to its four neighbors. Applications include collision avoidance for self-driving cars, shortest path planning, and scientific computing, and are shown to be scalable across many cores. The chip achieves 559 million traversed edges per second at 105x improved energy efficiency compared with existing platforms such as field-programmable gate array and CPU. The processor operates nominally at 1.79 ns per node with peak power consumption of 26.4 mW.