[Octave-bug-tracker] [bug #61732] news unclear

[Markus Mützel]

Update of bug #61732 (project octave):

                Category:                    None => Documentation          
                  Status:                    None => Invalid                
             Open/Closed:                    Open => Closed                 

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Follow-up Comment #1:

Afaict, there is no unique solution to (nearly) singular square matrix
equations. Instead, `mldivide` returns an "arbitrary" (but hopefully
numerically close) solution `x` that minimizes `norm(A*x-b)`.
In prior version, Octave used an algorithm for which the solution `x` had a
minimum norm `norm(x)`. That's what is called a "minimum-norm solution" IIUC.
In newer versions, it'll use an LU factorization to minimize `norm(A*x-b)`.
That will return a different solution `x`. Afaict, that solution won't
(necessarily) have the minimum norm of all possible solutions. But it happens
to be more numerically stable(?). I.e., the norm of `A*x-b` will more likely
be smaller than using the solution `x` calculated in previous versions of
Octave in that equation.

I don't think that note is contradicting itself. But, it's important to
distinguish between `norm(A*x-b)` and `norm(x)` (which can be minimized at the
same time or not...).

Closing as invalid.

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