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IDProjectCategoryView StatusDate SubmittedLast Update
0029271CommunityOCCT:Modeling Datapublic2017-10-27 17:442017-11-07 11:18
ReporterMauro Mariotti Assigned Tobugmaster  
PrioritynormalSeverityminor 
Status closedResolutionno change required 
PlatformWindowsOSVC++ 2015 
Product Version7.1.0 
Summary0029271: missing factor in function gradient
DescriptionIn functions Gradient and Values
of class Extrema_FuncDistSS
file Extrema_GenExtSS.cxx
I think that a "2" factor is missing:

the function is d(u,v,s,t) = (P(u,v) - Q(s,t)) . (P(u,v) - Q(s,t))

so the u derivative should be

2 * (P - Q) * dP/du
TagsNo tags attached.
Test case number

Relationships

related to 0029289 closedbugmaster Wrong derivatives in math_TrigonometricFunctionRoots.cxx file 

Activities

aml

2017-10-30 13:48

developer   ~0071845

Mathematically, you are right but in this algorithm, it is not needed. Coefficient only affects the magnitude of the first derivative but it does not affect the direction. A calculated derivative is used in step estimation (one-dimensional optimization problem), so coefficient can be omitted (as it is done in current implementation).

Mauro Mariotti

2017-11-02 12:22

reporter   ~0071929

Looking at math_BFGS.cxx (of my version, which is 6.6.0) I saw some use of the derivative (not just its direction), to find the bracketing values.
Then the minimum is found using only the function values.
Anyway you know it better than me, for me you can close the issue

aml

2017-11-02 12:29

developer   ~0071932

Several improvements in math_BFGS have been made over years. Your version of the occt is outdated.

aml

2017-11-02 12:57

developer   ~0071934

Dear msv,
It is proposed to close this issue.

msv

2017-11-02 17:04

developer   ~0071953

I agree.

Issue History

Date Modified Username Field Change
2017-10-27 17:44 Mauro Mariotti New Issue
2017-10-27 17:44 Mauro Mariotti Assigned To => msv
2017-10-30 13:48 aml Note Added: 0071845
2017-10-30 14:57 msv Assigned To msv => Mauro Mariotti
2017-10-30 14:57 msv Status new => feedback
2017-11-02 12:22 Mauro Mariotti Note Added: 0071929
2017-11-02 12:29 aml Note Added: 0071932
2017-11-02 12:57 aml Assigned To Mauro Mariotti => msv
2017-11-02 12:57 aml Note Added: 0071934
2017-11-02 17:04 msv Note Added: 0071953
2017-11-02 17:04 msv Assigned To msv => bugmaster
2017-11-02 17:54 abv Relationship added related to 0029289
2017-11-07 11:18 bugmaster Status feedback => closed
2017-11-07 11:18 bugmaster Resolution open => no change required