Pathways is a single-controller distributed training system designed to coordinate large-scale model training across multiple accelerator groups by representing computations as a global dataflow graph. Unlike traditional SPMD models like DDP and FSDP that rely on synchronous collectives, Pathways uses asynchronous dispatch and a central scheduler to maximize hardware utilization and prevent deadlocks in complex workloads. By decoupling model definition from physical hardware via virtual devices, developers can efficiently scale complex training architectures and seamlessly handle dynamic workloads like reinforcement learning post-training.
