Merlin Framework Targets HPC ML Workflows
The Merlin framework is being developed to orchestrate large-scale, distributed machine learning workflows in high-performance computing (HPC) environments. The open-source project enables multi-machine and queue-based model training, which is critical for complex risk modeling and pricing simulations. Key features include provenance tracking for auditability and robust checkpointing to reduce downtime during long-running jobs.
- The framework is a component of the broader Workflow Enablement and AdVanced Environment (WEAVE) project at Lawrence Livermore National Laboratory (LLNL), which provides a suite of open-source tools for HPC applications. - Merlin is built as an extension of another LLNL tool, Maestro, which provides the YAML-based specification for defining the workflow's steps and dependencies. For execution, it uses Celery as a distributed task queue and can interface with resource managers like Flux, another LLNL project designed for next-generation HPC systems. - A key architectural distinction from more general-purpose orchestrators like Apache Airflow is Merlin's use of a persistent, external queue server decoupled from the HPC system's nodes. This design allows for massive ensembles of simulations—in one case, 100 million individual simulations for an inertial confinement fusion study on the Sierra supercomputer. - While Airflow is a versatile, task-based orchestrator with a rich set of connectors for various systems, Merlin is purpose-built for scenarios requiring near-linear scaling of many small, similar simulations, which is common in scientific modeling and could be applied to large-scale Monte Carlo simulations in financial risk analysis. - The underlying resource management framework, Flux, which Merlin is designed to leverage, offers a hierarchical approach to scheduling. This allows a large resource allocation to be subdivided and managed by nested Flux instances, enabling higher throughput for large ensembles of jobs than traditional schedulers. - Application examples are primarily from the physical sciences, including modeling for inertial confinement fusion, extreme ultraviolet light generation, and atomic physics, demonstrating its capability in handling complex, multi-modal physics-based data.
