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FindRoot question

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

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...)

--j

-- 
Jonathan Greenberg
Graduate Group in Ecology, U.C. Davis
http://www.cstars.ucdavis.edu/~jongreen
http://www.cstars.ucdavis.edu
AIM: jgrn307 or jgrn3007
MSN: jgrn307 at msn.com or jgrn3007 at msn.com