IBBM 2017

Optimization has issues if you add parameters to subsequent runs
issueid=723 07-07-2015 09:24 AM
Optimization has issues if you add parameters to subsequent runs
Optimization has issues if you add parameters to subsequent runs

I have been experimenting with FEBio to determine the material parameters for a biphasic, viscoelastic model that uses the Ogden unconfined material for the solid phase. I have been playing around with some simulated data I created by running the forward simulation, and seeing how well the optimization model can determine the parameter values I used to generate the simulated data.

Because the model has 7 material parameters, I started with trying to determine c1 and cp of the Ogden material with the others as being given (first case). Once those converged, I wanted to additionally determine the m1 parameter of the Ogden material (second case), and this is when issues developed. Specifically, I launched FEBio2, and using FEBio2's prompt, I ran the optimization for the first case. This execution is shown in lines 36 - 5338 of the attached log file. Then, keeping FEBio2 running, I edited the optimization feb file in a text editor and then re-ran the optimization from FEBio2's prompt. This execution in shown in lines 5346 - end. You can see in line 8200 how the guessed parameters go bad and in line 11061 how they do not fall within the range given with the optimization feb file.

If I terminate FEBio2 and run the modified optimization (second case), then there are no problems, so there is an easy way to avoid this. However, FEBio2 seems to buffer something between optimization runs that is causing problems.
Issue Details
Issue Number 723
Project FEBio
Category Unknown
Status Fixed
Priority Unknown
Affected Version Unknown
Fixed Version (none)
Users able to reproduce bug 0
Users unable to reproduce bug 0
Assigned Users (none)
Tags (none)

08-04-2015 10:36 AM
Hi Joshua,

We were preoccupied with the IBBM summer course in July, so I apologize for not replying to this earlier. I'll let you know what I figure out.



08-12-2015 01:20 PM
Hi Joshua,

This bug has been fixed and will be updated in the next release.



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