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FindRoot question

  • To: mathgroup at
  • Subject: [mg48596] FindRoot question
  • From: Jonathan Greenberg <greenberg at>
  • Date: Sat, 5 Jun 2004 19:58:20 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

I'm using "Rayica", a ray-tracing algorithm for Mathematica, and as part of
the calculations it performs it uses FindRoot.  I get the following error:

FindRoot::lstol: The line search decreased the step size to within tolerance
specified by AccuracyGoal and PrecisionGoal but was unable to find a
sufficient decrease in the merit function.  You may need more than
MachinePrecision digits of working precision to meet these tolerances.

Can anyone tell me if Mathematica returns a "best guess" if this error
occurs, or does it report an error (and no value is returned)?  Can I modfiy
the tolerance on a global scale (the FindRoot calls are buried in the
add-in, so it would be very difficult for me to find them...)


Jonathan Greenberg
Graduate Group in Ecology, U.C. Davis
AIM: jgrn307 or jgrn3007
MSN: jgrn307 at or jgrn3007 at


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