[Octave-bug-tracker] [bug #64347] qp (quadratic programming) error code 2 not preperly described

[Julien Bect]

URL:
  <https://savannah.gnu.org/bugs/?64347>

                 Summary: qp (quadratic programming) error code 2 not preperly
described
                   Group: GNU Octave
               Submitter: jbect
               Submitted: lun. 26 juin 2023 07:33:35
                Category: Documentation
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Documentation
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: stable
         Discussion Lock: Any
        Operating System: Any
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: lun. 26 juin 2023 07:33:35     By: Julien Bect <jbect>
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)".








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