Warning that "Simulation with phi=[] could not be completed" occurred during 'Fit Data' task

I estimated 8 parameters of my glucose-insulin kinetics model(modified model of 'insulindemo.sbproj') using glucose concentration data as response and glucose, insulin doses as input dose data. The estimation was done by 'Fit Data' task of SimBiology. However, there was warning with details; "Simulation with phi = [222.249598314537 144.778388565053 2.3665676931561 0.00609950427451014 0.156172487611996 0.0142886095746218 0.00444912107474936 1.27397631652191] could not be completed because: Integration Tolerance Not Met. Empty results have been returned for this simulation." I used 'ode15s(stiff/NDF) solver with RelativeTolerance value of 1.0E-6. and estimation method was 'ga(Constrained optimization using genetic algorithm)' with TerminationTolerance of 1.0E-10 and MaximumGeneration of 800. What is the meaning of this warning message? and how could I treat it? Thank you for your interest.

Answer 1

[Arthur Goldsipe]

You can likely ignore this warning. It means that during parameter estimation, the genetic algorithm selected a "bad" set of parameter values. These parameter values were "bad" because they resulted in a system of differential equations that could not be integrated to the specified tolerances. This often means one or more of the parameter values are extremely large or extremely small. If you see this warning repeatedly during a 'Fit Data' task, you might want to change the parameter bounds used during estimation to avoid extremely large or small parameter values that lead to integration errors.