Re: No Invert Functions?

"Michael A. Koerber" <[email protected]> Thu, 26 Sep 2002 09:25:06 -0400

Newsgroups	gmane.lisp.matlisp.user
Message-ID	<[email protected]>

Nicolas,

1.  (M/ A) eventually calls (GESV A I), where I is the identity
    matrix, which intern calls the FORTRAN ?GESV which performs the LU
    decomposition on the system of equations [A I] to form the inverse
    of A.

2.  Your statement concerning inverses is correct...and it is correctly 
    implimented in MATLISP.

> The point is that computing the inverse is often not recommended
> because of numerical stability.  Usually one uses the LU decomposition
> directly which is done by the getrf/getrs-pair.  Of course, if you
> only need to apply the inverse once you could be satisfied with m/.
> 


mike
**************************************************
Dr Michael A. Koerber    	Micro$oft Free Zone
MIT/Lincoln Laboratory