bugGNU Octave - Bugs: bug #64347, qp (quadratic programming) error...

 
 

bug #64347: qp (quadratic programming) error code 2 not preperly described

Submitter:  Julien Bect <jbect>
Submitted:  Mon 26 Jun 2023 07:33:35 AM UTC
   
 
Category:  Documentation Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Documentation
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * stable Operating System:  * Any
Fixed Release:  None Planned Release:  None
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Mon 26 Jun 2023 08:35:53 AM UTC, comment #1: 

This issue is probably related to the recent introduction of the 'isdefinite' check (https://hg.savannah.gnu.org/hgweb/octave/rev/2f1fae9dd79d), which changed the meaning of error code 2.

Related doc issue: https://savannah.gnu.org/bugs/?64348

Julien Bect <jbect>
Mon 26 Jun 2023 07:33:35 AM UTC, original submission:  

The documentation of qp writes that error code 2 occurs when "The problem is not convex and unbounded", which is not correct.

Looking at the source code, it appears that qp fails with info=2 when the matrix H is not Hermitian positive definite (lines 351-353):


if (isdefinite (H) != 1)
  info = 2;
endif


It is true that in this case the problem is not convex.

It is not true that is is necessarily unbounded (it may remain bounded thanks to the constraints).

Suggested fix: remove "and unbounded" in the description of error code 2, "convex" is enough.

Alternative: write "(and possibly unbounded)".

Julien Bect <jbect>

 

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