Re: Improving sqrtm

[Carnë Draug]

On 16 February 2016 at 17:11, Nicholas Jankowski <address@hidden> wrote:
> On Tue, Feb 16, 2016 at 11:45 AM, Mudit Sharma <address@hidden>
> wrote:
>>
>> Indeed that would be against the spirit of open-source.
>> I provided the sqrtm link so as to make it some informative for the
>> readers/maintainers.
>> Infact the improved sqrtm will be based on Higham's latest work on sqrtm
>> which
>> dates back to 1999
>> (www.maths.manchester.ac.uk/~higham/narep/narep336.ps.gz)
>> and Matlab still uses work previous than the latest algorithm proposed in
>> 1999.
>>
>> Higham's work on sqrtm in 1999 will be the basis for the improved sqrtm
>> and not on Matlab's
>> work.
>>
>> Bests,
>> Mudit
>>
>>
>> On Tue, Feb 16, 2016 at 9:31 PM, John W. Eaton <address@hidden> wrote:
>>>
>>> On 02/16/2016 03:10 AM, Mudit Sharma wrote:
>>>>
>>>> All,
>>>> I'm improving sqrtm in Octave and want to align it with
>>>> the sqrtm from Matlab which has 3 output arguments,
>>>> whereas the existing sqrtm.cc from octave has 2 .
>>>>
>>>> Here's the link for sqrtm from Matlab:
>>>> https://github.com/RickOne16/sqrtm/blob/master/sqrtm.m
>>>>
>>>> and this is octave's sqrtm:
>>>> https://github.com/RickOne16/sqrtm/blob/master/sqrtm.cc
>>>>
>>>> How do I change the octave's sqrtm code to align it with that
>>>> from Matlab which has 3 output arguments?
>>>
>>>
>>> One thing you can't do is use the code you've linked to as a basis for
>>> your changes.  That code clearly has a MathWorks copyright notice on it.  So
>>> now I'm not likely to accept any changes from you related to this function.
>>>
>>> If you want to contribute to the development of Octave it is critical
>>> that the work you do is your own, or that it is based on free software.
>>>
>>> jwe
>>>
>>
>
> Generally speaking, we should be able to pull most necessary information
> from public-facing help files, Matlab's public documentation, or user
> reports of behavior. The concern is copyright. Math is public domain.
> Software algorithms can be copyrighted. Copyright involves legal concerns.
> Even using copyrighted code as a reference before writing your own can be
> problematic. John's concern is valid, as he has to maintain integrity of the
> codebase.
>
> Nick J.

To everyone involved. I have attached the last implementation of sqrtm by Higham
before Mathworks.  I have received this file straight from Higham
himself last year.

Carnë

sqrtm2.m
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