[ADMB Users] Oscillating likelihood values?

[Mark Maunder]

You might want to check your model using the derivative checker to make
sure that you have not included code for which the derivative can't be
calculated.

 

Mark

 

<http://www.fisheriesstockassessment.com/TikiWiki/tiki-index.php?page=Sp
atial+Analysis+for+Stock+Assessment+2008> 

 

Mark Maunder 

Head of the Stock Assessment Program

Inter-American  Tropical Tuna Commission
8604 La Jolla Shores Drive
La Jolla, CA, 92037-1508, USA
  
Tel: (858) 546-7027
Fax: (858) 546-7133
mmaunder at iattc.org
http://www.fisheriesstockassessment.com/TikiWiki/tiki-index.php?page=Mar
k+Maunder <http://iattc.org/iattc-staffMMaunder.htm> 

 

Visit the AD Model Builder project at
 http://admb-project.org/ <http://admb-project.org/> 

 

See the following website for information on fisheries stock assessment

http://www.fisheriesstockassessment.com/

 

________________________________

From: users-bounces at admb-project.org
[mailto:users-bounces at admb-project.org] On Behalf Of John
Sent: Thursday, January 14, 2010 6:56 AM
To: users at admb-project.org
Subject: [ADMB Users] Oscillating likelihood values?

 

Hi

 

I have been browsing through the manuals and posts on the ADMB site, but
could not find a reference to what I am experiencing at the moment with
my code. The likelihood value seems to be oscillating between two
values, 'A' and 'B', with the distance between the values increasing
slightly with each iteration. It would look something like this:

15

  18

14.5

  18.5

14

  19

13.5

  19.5

 

It keeps on doing this for several iterations, and then gives the
"Function minimizer: step size too small - ialph=1" error. Is there
anything in particular that I can do to pinpoint the problem? I have
disabled all but one of the model parameters, yet the problem persists.
I have even tried other model parameters, one at a time, but to no
avail.

 

Any advice would be very welcome!

 

Regards,

John E. Murray

OLRAC

Silvermine House, Steenberg Office Park.

Tokai 7945, Cape Town, South Africa.

Office +27 (0)21 702 4111

Fax +27 (0)21 702 4333

Email - john at olrac.com

 

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