bugGNU Octave - Bugs: bug #33887, LU Factorization cannot give a...

 
 

bug #33887: LU Factorization cannot give a desired order of lower matrix

Submitter:  Ben <verilog>
Submitted:  Sat 30 Jul 2011 04:54:18 AM UTC
   
 
Category:  None Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Invalid / Not an Octave Bug Assigned to:  None
Originator Name:  verilog Open/Closed:  * Closed
Release:  * 3.2.4 Operating System:  * Microsoft Windows
Fixed Release:  None Planned Release:  None
* Mandatory Fields

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Sat 30 Jul 2011 05:27:01 AM UTC, comment #1: 

Not a bug. The LU factorisation may pivot. If you want the pivoting in a separate matrix, you need to request it. Try


[l, u, p] = lu(a)


instead.

Jordi GutiƩrrez Hermoso <jordigh>
Group Member
Sat 30 Jul 2011 04:54:18 AM UTC, original submission:  

I'm not sure if it is a bug

a = [ 1 2 1;
          2 1 2;
          1 2 3 ]
[ l, u ] = lu(a)

output:
l=
  0.50000 1.00000 0.00000
  1.00000 0.00000 0.00000
  0.50000 1.00000 1.00000

what I expect:
l=
  1.00000 0.00000 0.00000
  0.50000 1.00000 0.00000
  0.50000 1.00000 1.00000

Thanks!

Ben <verilog>

 

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Attached Files
file #23713:  test.m added by verilog (43B - text/plain)

 

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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2011-07-30 jordigh StatusNone Invalid / Not an Octave Bug
        Open/ClosedOpen Closed
    2011-07-30 verilog Attached File- Added test.m, #23713
        Carbon-Copy- Added -email is unavailable-

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