Simulation accuracy

[Pia Stefanek]

Hi,

When I perform OpenSim simulations as for example with the CMC tool, how do I know if the output deviations arise from simulation errors (due to inaccuracy) or if they refer to 'real' differences?

When I perform CMC with the same input files, the output files will be slightly different due to simulation errors. When I perform CMC with different input files, the output files will also be different. But how do I know which deviations refer to simulation inaccuracy and which not?

Thank you very much!
Pia

[Thomas Uchida]

The CMC setup file lists values for properties like integrator_error_tolerance, optimizer_convergence_criterion, and optimizer_max_iterations that control the precision of the simulation. If you are concerned about precision, you could perform a convergence analysis or explore the sensitivity of your results when these parameters are tightened/relaxed.

[Pia Stefanek]

Could somebody explain me the Optimizer convergence criterion? I really tried to understand it but I could not find any writings About it related to OpenSim. I understand that CMC uses an Integrator and this Integrator compares the state values at each time step. But what does the convergence criterion indicate?