[Octave-bug-tracker] [bug #66511] CXSPARSE library does not compute 3-output qr()

[Rik]

URL:
  <https://savannah.gnu.org/bugs/?66511>

                 Summary: CXSPARSE library does not compute 3-output qr()
                   Group: GNU Octave
               Submitter: rik5
               Submitted: Mon 02 Dec 2024 10:32:55 AM PST
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: Confirmed
             Assigned to: None
         Originator Name:
        Originator Email:
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any
           Fixed Release: None
         Planned Release: 10.1.0 (current default)


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 02 Dec 2024 10:32:55 AM PST By: Rik <rik5>
The qr() function in Octave can be calculated EITHER by the SPQR and CHOLMOD
libraries OR the CXSPARSE library.

However, when using CXSPARSE the third argument (permutation matrix or vector)
is not calculated.

Example code:


[q,r,p] = qr (speye (3))
q =

  -1   0   0
   0  -1   0
   0   0  -1

r =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3 [33%])

  (1, 1) -> -1
  (2, 2) -> -1
  (3, 3) -> -1

p = Compressed Column Sparse (rows = 0, cols = 0, nnz = 0)



Either Octave is not using the API correctly and not recovering the
permutation matrix from CXSPARSE.  Or CXSPARSE does not calculate it.  If it
is not calculated then Octave should produce a warning about how the feature
is not available due to choices of which libraries were used at configuration
time.







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