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Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: Optimization
Replies: 6   Last Post: Feb 27, 2013 10:42 AM

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Matt J

Posts: 4,992
Registered: 11/28/09
Re: Optimization
Posted: Nov 21, 2012 5:18 PM
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"Carlos Alejandro Perez Lasso" <carlosalejandro85@gmail.com> wrote in message <k8jaks$fqr$1@newscl01ah.mathworks.com>...
> Hi Matlab users,
>
> My purpose is to use the Optimtool to estimate material model parameters so that running the model with such parameters in Abaqus results in a predicted curve close to some experimental data.
> I am trying to solve the problem with the lsqnonlin solver

============

If it's a curve fitting problem, mightn't it be better to use lsqcurvefit.


> Optimization completed because the size of the gradient at the initial point
> is less than the default value of the function tolerance.

==========

This usually occurs because you have quantizing operations like ROUND, FLOOR, CEIL, etc... in your objective function. They make the function locally flat in places, making the initial point trivially a point of zero gradient.



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