MUSCLE3: The Multiscale Coupling Library and Environment

MUSCLE3 0.7.1

MUSCLE3 is the third incarnation of the Multiscale Coupling Library and Environment, and the successor to MUSCLE 2. Its purpose is to make creating coupled multiscale simulations easy, and to then enable efficient Uncertainty Quantification of such models using advanced semi-intrusive algorithms.

MUSCLE3 uses the Multiscale Modelling and Simulation Language (MMSL) to describe the structure of a multiscale model. MMSL can be expressed in the form of a diagram (gMMSL; not yet implemented) or as a YAML file (yMMSL; this is convenient both for people and for software). The MMSL lets one describe which components (submodels, scale bridges, data converters, UQ components, etc.) a multiscale model consist of, how many instances of each we need, and how they are wired together.

MUSCLE3 is intended to scale from your laptop to the exascale. At the low end, it supports a non-distributed but parallel mode in which an entire multiscale simulation, including all component implementations and the MMSL configuration, is in a single (short) Python file. Next is a distributed mode where the manager and component instances run on multiple nodes in a cluster, and communicate directly with one another. Beyond that, additional components and optimisations are envisioned that would allow scaling to huge machines or combinations of multiple machines. Our goal is to make the transitions between these modes as smooth as possible, so that extra compute power can be added gradually, as needed.

• Support for Python 3.11 (working already, now official)
• Enabled type checking support for the libmuscle Python API

• Easier crash debugging due to improved root cause detection
• Fixed crash in profiling timeline plot
• Better performance of timeline plot
• Better visual quality of timeline plot
• Improved profiling of shutdown process
• Fixed crash in profiler for large simulations
• Fixed several (harmless) compiler warnings
• Small documentation rendering improvements

• David for reporting many of these and submitting a fix too!