The following Simulator solver algorithms are available for fitting exercises:

• Backwards Euler
• Rosenbrock (Default)
• LSODA.

Your choice of solver algorithm should be made on the basis of run-time in simulator using the Integration Method dropdown in the Advanced Options window (click  to open). In general, the default routine (Rosenbrock) will be adequate, but occasionally one of the other solver routines will be faster, reducing run times, or more robust.

The solver accuracy can also be set using the Accuracy dropdown. The default accuracy (0.001) is normally sufficient, but this can be adjusted, e.g. if higher accuracy was required when running in simulator. Available accuracies range from 0.01 to 1x10^-8.