GNU Octave - Bugs: bug #65054, inv (x) should return same results...

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bug #65054: inv (x) should return same results for exceptional matrices regardless of form of matrix, and agree with rcond

Submitter:	Rik <rik5>
Submitted:	Tue 19 Dec 2023 11:31:40 PM UTC


Category:	Octave Function	Severity:	3 - Normal
Priority:	5 - Normal	Item Group:	Other
Status:	In Progress	Assigned to:	rik5
Originator Name:		Open/Closed: *	Open
Release: *	dev	Operating System: *	Any
Fixed Release:	None	Planned Release:	10.1.0 (current default)

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Wed 20 Dec 2023 07:54:52 PM UTC, comment #3: This is so big I started a Discourse thread on the topic: https://octave.discourse.group/t/exceptional-value-input-to-octave-blas-lapack-functions/5105	Rik <rik5>
Wed 20 Dec 2023 06:06:26 PM UTC, comment #2: This is the paper describing the direction lapack is moving wrt those issues: https://arxiv.org/pdf/2207.09281.pdf just fyi. Dmitri. --	Dmitri A. Sergatskov <dasergatskov>
Wed 20 Dec 2023 04:25:08 PM UTC, comment #1: I reviewed the code for inverse and the problems run much deeper. There are three different routines for calculating the inverse and they all need to be made consistent with each other and with the results of calling rcond() directly. Changing bug title to reflect this.	Rik <rik5>
Tue 19 Dec 2023 11:31:40 PM UTC, original submission: For consistency, the inverse of a singular matrix should return all Inf. For example, inv (1e22*ones(2,2)) warning: matrix singular to machine precision ans = Inf Inf Inf Inf Currently Octave usually returns all NaN matrix along with an rcond of NaN. However, this depends on the version of BLAS being used. Such a dependency is undesirable as well as being the wrong result.	Rik <rik5>

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Date	Changed by	Updated Field	Previous Value	=>	Replaced by
2023-12-20	rik5	Release	stable		dev
2023-12-20	rik5	Summary	inv (Inf (2,2)) should return matrix of all Inf and rcond of 0		inv (x) should return same results for exceptional matrices regardless of form of matrix, and agree with rcond

GNU Octave - Bugs: bug #65054, inv (x) should return same results...

bug #65054: inv (x) should return same results for exceptional matrices regardless of form of matrix, and agree with rcond

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