OpenModelica — Simulator

Modelica model
Initial conditions & parameters
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Run a model to see results.
Documentation
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Simulation settings
Stop time
Intervals
Integration method -s
Tolerance
Nonlinear solver -nls
NLS linear solver -nlsLS
Linear solver -ls
Sparse linear solver -lss
Log streams -lv

Solver selectors and log streams are read at each run, so changing one re-simulates without recompiling. The model's output goes to the browser console.

Export FMU
Interfaces
Model Exchange Co-Simulation
CS solver

FMI 3.0 wasm component. Co-Simulation embeds the solver; Model Exchange leaves integration to the importer.