title: Matlab minimization problem: finding a hole in a flat surface
body: <p>My 2D objective function is like finding a whirlpool in the surface of a lake.  I do not have good initial guesses.  Below example is in the middle of the surface but it may be anywhere on the surface and the diamerter may be smaller than shown in the example.</p>
  <p><a href="https://i.stack.imgur.com/xiVbJ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xiVbJ.png" alt="enter image description here" /></a></p>
  <p>I was thinking that MATLAB fminsearch would work but if the initial guess is on the flat surface, it will go a short distance then  stop (shown by the dots on the left which increase in size as iteration count goes up.).
  I was thinking that if I could increase the multiplier of the search (1.05 by default), I could better set up the problem with an initial guess in the center of the surface and a large spread of the trial points.  But I find that there is no option to change the multiplier used in fminsearch.
  Does anyone have a suggestion for how to better approach this minimization problem in MATLAB?</p>