Public bug reported:
Binary package hint: octave2.9
In specific cases, the left division in octave 2.9 seems to ignore the below
diagonal elements e,g:
octave2.9:1> y=[ 1; 2 ]
y =
1
2
octave2.9:2> A=[1 0; 0 1]
A =
1 0
0 1
octave2.9:3> A\y
ans =
1
2 <-- correct
octave2.9:4> A(2,1)=0.5;
octave2.9:5> A\y
ans =
1
2 <-- incorrect!
octave2.9:10> A
A =
1.00000 0.00000
0.50000 1.00000
Note that if A is initialised directly as A=[1 0;0.5 1], the bug does not
manifest itself.
It seems as if some strange over-optimisation takes place and assumes A is
upper triangular no matter what we do to it later (if the changed element is
above diagonal, the results are correct).
Tested on up to date feisty
** Affects: octave2.9 (Ubuntu)
Importance: Undecided
Status: New
--
Octave 2.9 left division gives incorrect results
https://bugs.launchpad.net/bugs/132430
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