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Re: new gsvd function incompatible w/Matlab
From: |
Rik |
Subject: |
Re: new gsvd function incompatible w/Matlab |
Date: |
Wed, 17 Aug 2016 09:22:57 -0700 |
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