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From: Marcelo Marazzi <mREMOVEmaALLraCAPITALSzzi@mathworks.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Line search failing?
Date: Fri, 15 Aug 2008 16:31:49 -0400
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Dave,

Possible reasons are that the line search algorithm failed
because the objective function is not differentiable. Or
because roundoff errors are stalling convergence of the line
search algorithm.

Is it possible to post the objective? If it's not, you
may want to send the data needed to reproduce the problem to
tech support http://www.mathworks.com/support/

-Marcelo

David Doria wrote:
> I am using fminunc to try to find the minimum of a function.
>  I plotted the function (it is only 2d) and it seems
> extremely well behaved - visually it there is without a
> doubt a single local min if you start any where near the min
> value (the value is at (20, 0) and there looks to be about a
> 5 unit radius of convergence).
> 
> However, when I run fminunc, I get:
> 
> Line search cannot find an acceptable point along the
> current search direction.
> 
> The only thing I could think to check is if the gradient was
> somehow 0-ish even though it didn't look like it in the
> plot, but when I output the gradient at the iteration it
> gives the error it is
> 
> Gradient is: 
> 
> ans =
> 
>    -1.2747
>     0.4237
> 
> Does anyone know what else to check to see why line search
> can't find a good point?
> 
> Thanks,
> 
> Dave