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[Octave-bug-tracker] [bug #42418] luupdate transposes permutation matrix


From: David Spies
Subject: [Octave-bug-tracker] [bug #42418] luupdate transposes permutation matrix if not constructed properly
Date: Sat, 24 May 2014 19:15:06 +0000
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:29.0) Gecko/20100101 Firefox/29.0

URL:
  <http://savannah.gnu.org/bugs/?42418>

                 Summary: luupdate transposes permutation matrix if not
constructed properly
                 Project: GNU Octave
            Submitted by: dspyz
            Submitted on: Sat 24 May 2014 07:15:05 PM GMT
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

    _______________________________________________________

Details:

If the permutation matrix input is constructed as a column permutation, then
luupdate returns a different result than if constructed as a row permutation:
        

     A = [0.091364  0.613038  0.999083;
          0.594638  0.425302  0.603537;
          0.383594  0.291238  0.085574;
          0.265712  0.268003  0.238409;
          0.669966  0.743851  0.445057 ];
     
     u = [0.85082;
          0.76426;
          0.42883;
          0.53010;
          0.80683 ];
     
     v = [0.98810;
          0.24295;
          0.43167 ];
     
     [L,U,P1] = lu (A);
     P2 = eye(5)(:,[2,3,5,4,1]);
     
     P1 == P2 #True
     [L,U,RP1] = luupdate (L,U,P1,u,v);
     [L,U,RP2] = luupdate (L,U,P2,u,v);
     RP1 == RP2 #False







    _______________________________________________________

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  <http://savannah.gnu.org/bugs/?42418>

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