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NEWTON: Roundoff problem in lnsrch_d [message #91062] Fri, 29 May 2015 11:14 Go to next message
Nikola is currently offline  Nikola
Messages: 53
Registered: November 2009
Member
I'm solving a system of equations using the intrinsic NEWTON function. For many cases it work fine, but for some cases my code is crashing with a bit cryptic message:

NEWTON: Roundoff problem in lnsrch_d

I can't google anything on it. Any clues where to look? I guess it indicates a convergence problem, still it's difficult to diagnose what's going on without understanding the message (and without going step by step through NEWTON).

Thanks!

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Re: NEWTON: Roundoff problem in lnsrch_d [message #91064 is a reply to message #91062] Fri, 29 May 2015 13:19 Go to previous messageGo to next message
Russell[1] is currently offline  Russell[1]
Messages: 101
Registered: August 2011
Senior Member
On Friday, May 29, 2015 at 2:14:45 PM UTC-4, Nikola Vitas wrote:
> I'm solving a system of equations using the intrinsic NEWTON function. For many cases it work fine, but for some cases my code is crashing with a bit cryptic message:
>
> NEWTON: Roundoff problem in lnsrch_d
>
> I can't google anything on it. Any clues where to look? I guess it indicates a convergence problem, still it's difficult to diagnose what's going on without understanding the message (and without going step by step through NEWTON).
>
> Thanks!

I have no idea what the error means, but just to be clear what options are you using? Double? Tolerence? etc.

-R

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Re: NEWTON: Roundoff problem in lnsrch_d [message #91066 is a reply to message #91064] Fri, 29 May 2015 15:03 Go to previous messageGo to next message
Nikola is currently offline  Nikola
Messages: 53
Registered: November 2009
Member
I use /double. I varied tolerances and the number of iterations, but the result, i.e. the error was the same.

The values in the problem may vary for many orders of magnitude and I'm not surprised that the algorithm does not converge for certain conditions. However, I don't know how to capture this error and to continue with execution of other cases when it happens.

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Re: NEWTON: Roundoff problem in lnsrch_d [message #91067 is a reply to message #91066] Fri, 29 May 2015 16:30 Go to previous message
Matthew Argall is currently offline  Matthew Argall
Messages: 286
Registered: October 2011
Senior Member
Can you provide a short example that causes the error?

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