RE: [Lapackpp-devel] Tested LaLinearSolve(LaGenMatDouble, LaGenMatDouble &, LaGenMatDouble) ?

[Jacob \(Jack\) G. <jg...@cs...>]

I tried it out again with both square and non-square matricies on both
complex and doubles:

Results are the same for both Complex matricies and Doubles.

With square matrices, the results are more viable.  The equation AX=B, with
A and B being the same, X should return the identity matrix; however it does
not.  Although through multiplying AX, the result still is B.  

With rectangular matrices, the results are the same in both complex and
doubles, but AX != B;  X is usually all 0's, or very close to 0's (10e-300).

Any thoughts?

Jack

-----Original Message-----
From: lap...@li...
[mailto:lap...@li...] On Behalf Of Jacob
(Jack) Gryn
Sent: August 10, 2004 9:31 AM
To: 'Christian Stimming'
Cc: lap...@li...
Subject: RE: [Lapackpp-devel] Tested LaLinearSolve(LaGenMatDouble,
LaGenMatDouble &, LaGenMatDouble) ?

I'll look into it some more later today when I get a chance, keep in mind
that the code runs differently for square matrices (calls the
LaLULinearSolve function) vs non-square matrices (calls the
LaQRLinearSolve).

I remember that my resulting matrix, X, only had values in the leftmost
column, and all were in the order of 10^-306 (I've never seen such small
numbers in my life :) ) when matlab's \ operator gave be good results.  I'll
try the same thing with complex matrices to see what happens, maybe I'm
doing something wrong.

Jack

-----Original Message-----
From: Christian Stimming [mailto:sti...@tu...]
Sent: Tuesday, August 10, 2004 4:09 AM
To: Jacob (Jack) Gryn
Cc: lap...@li...
Subject: Re: [Lapackpp-devel] Tested LaLinearSolve(LaGenMatDouble,
LaGenMatDouble &, LaGenMatDouble) ?

Hi,

Jacob (Jack) Gryn schrieb:
> ps. if you haven't noticed, I posted the row-order changes to cvs last 
> night.

Yes, thanks a lot. This looks very nice. I have noticed and I also added
some more documentation in the header.

 > I've been trying to solve a matrix equation Ax=b with all 3 variables,  >
A,x, and b, being LaGenMatDoubles.
 >
 > I've used tried the function LaLinearSolve(LaGenMatDouble,  >
LaGenMatDouble &, LaGenMatDouble), however, my results are clearly not  >
correct.  (Maybe I'm doing something wrong)  >  > Has this been tested?
I've noticed the tGenSolve.cc program does not  > contain a test for the
linear solve of 3 matricies.

I did not test the real-valued functions at all since I only use the
complex-valued matrices and functions. It may very well be that there is
some kind of bug. However, I would be quite surprised if this is the case
since the linear solve routines really do not contain any non-trivial
operations. Could you document the problem further? I know for sure the
LaLinearSolve with LaGenMatComplex works correct, either for vectors or for
matrices. Can you try for X and B vectors and then for some simple matrices?
Maybe you could post a simple example (3x3) here?

Christian




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