Re: new gsvd function incompatible w/Matlab

[Rik]

On 08/17/2016 09:05 AM, Daniel J Sebald wrote:
> On 08/17/2016 10:28 AM, Rik wrote:
>> All,
>>
>> I don't want to look a gift horse in the mouth, but the new gsvd function
>> doesn't calculate the same values as Matlab.  This is a shame, because no
>> one with existing Matlab gsvd code will switch to Octave unless it is clear
>> that they can get the same results.  I filed a bug report about it here
>> (https://savannah.gnu.org/bugs/index.php?48807).
>>
>> If we are lucky, it is simply a matter of recombining the outputs in a
>> different format, but I am not a linear algebra expert so I haven't tried.
>>
>> --Rik
>
> What is not the same?  (I haven't looked closely.)  Is it something like
> the order of generalized eigenvalues/vectors?
Order of outputs is different, which is easily fixed but still does need
fixing.  The real issue is that the calculated results are different.  I
suspect that we just need to combine our outputs in a certain way, maybe
multiply two of them together or take a transpose, in order to get the same
results as Matlab.

>
> What is important is that the function is consistent.  There is an
> example in the documentation:

I want more than self-consistentcy.  The function is consistent in that it
produces outputs and the %!test blocks pass.  But because it isn't
Matlab-compatible it won't get adopted.

> Note, the following error messages don't seem accurately descriptive:
>
>>> demo gsvd
> warning: demo: no function gsvd found
> warning: called from
>     demo at line 117 column 5
>
> [No function gsvd found?  I just called it.]
>
>>> test gsvd
> ????? gsvd is a built-in function
>
> [Built-in functions don't have tests?]
>
This works for me using run-octave

octave:1> demo gsvd
warning: demo: no demo available for gsvd
warning: called from
    demo at line 120 column 5
octave:2> test gsvd
PASSES 16 out of 16 tests

--Rik