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From "Olexiy Movchan (JIRA)" <>
Subject [jira] [Commented] (MATH-1144) LevenbergMarquardtOptimizer does not allow to change current point during optimization
Date Thu, 16 Oct 2014 14:44:33 GMT


Olexiy Movchan commented on MATH-1144:
-------------------------------------- package that is attached to this jira contains
test. This unit test verifies the fitting of 3d cylinder and validator can be used there.
But that's not very simple unit test.

> LevenbergMarquardtOptimizer does not allow to change current point during optimization
> --------------------------------------------------------------------------------------
>                 Key: MATH-1144
>                 URL:
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.3
>            Reporter: Olexiy Movchan
>              Labels: fitting
>             Fix For: 3.4
>         Attachments:, MATH-1144.patch,,,
> It's a regression to commons-math v2.0.
> Our software uses LevenbergMarquardtOptimizer for surface fitting by sampled points.
Our parameterization of the surface we are fitting may be unconstrained, for example it is
enough to have only 4 variables to represent cylinder axis and origin (using euler angles
and origin distance), but to simplify derivative computation we instead use 6 parameter representation
(vector + point). To make sure that the we constrain our search to valid vectors and origins,
we need to renormalize and update surface parameters on every step of optimization.
> Please see this article for details of 3d surface fitting and parameter normalization:
> Attached package with 2 unit tests that reproduce this problem.
> Contents of package:
> 1) simple - simple single file test that tests only in/out side effect of patched library
> 2) full - complex test that fits cylinder using sampled points (uses cylinder, fit, utils
> 3) lib - contains commons-math3 jar libraries: v3.3 and v3.3A1 (patched). There are also
library sources.
> 4) patch - contains SVN patch file
> To reproduce:
> Run and tests with commons-math3-3.3.jar
OR commons-math3-3.3A1.jar libraries.

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