[Octave-bug-tracker] [bug #53440] Wrong factorization with ilutp type

[Marco Caliari]

URL:
  <http://savannah.gnu.org/bugs/?53440>

                 Summary: Wrong factorization with ilutp type
                 Project: GNU Octave
            Submitted by: caliari
            Submitted on: Fri 23 Mar 2018 01:31:47 PM UTC
                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: GNU/Linux

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Details:

According to the documentation (and matlab behavior) the following code


A=sprand(10,10,1/2);opts.type="ilutp";[L,U]=ilu(A,opts);norm(L*U-A,inf)


should give something like eps. In fact, droptol is zero, which means complete
LU factorization. The explicit pivoted version


A=sprand(10,10,1/2);opts.type="ilutp";[L,U,P]=ilu(A,opts);norm(L*U-P*A,inf)


works fine.




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