Re: [Matlisp-users] pseudoinverse

[Tunc S. <si...@ee...>]

Hi Mike.  This sounds good.  Will the function have to
work for A,B complex (or A real, B complex and so forth).
Thanks, Tunc


mak%koe...@ll... wrote:
> 
> Tunc,
> 
> 1.  Over the weekend I spent some more time on the PINV question.  In
> response to your question about DGELSD, the more I thought about it
> the more I liked it.  Since the routine accepts multiple RHS, I
> suppose it can be provided an identity matrix.  The result should then
> be the PINV matrix.  If I write something like this
> 
>   (DEFUN PINV (A &OPTIONAL (B NIL) (...))
>      ...
>      (LET ((B (IF (NULL B) IDENTITY-FOR-A B)))
>        ...
>        (CALLING-GELSD ...) ...))
> 
> then the user can say (PINV A) to get the psuedo-inverse,
> or they can say (PINV A B) to solve the multiple RHS problem.
> 
> 2.  The use of ?GELSD should aviod (my) concerns over differences in
> D1MACH values in a given CL implimentation and the associated FORTRAN.
> (BTW I found that the machine values are controlled by DLAMCH.F for
> LAPACK, not D1MACH.F as I thought.)
> 
> 3.  Due to current time constraints, I intend to:
> 
>     a. change the calling convention of PINV I posted last week to
>        provide this capability.  The computations remain essentially
>        unchanged.
> 
>     b. over the next few weeks, develop the ?GELSD.F wrappers and
>        replace the internals of PINV to use these.
> 
>     any thoughts or redirections concerning this?
> 
> mike
> 
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