[Scilab-Dev] empty sparse: sparse([]) vs sparse([],[],[0 0])

[Stéphane Mottelet]

Le 22/01/2019 à 17:06, Samuel Gougeon a écrit :
> Le 22/01/2019 à 16:34, Stéphane Mottelet a écrit :
>> Le 22/01/2019 à 16:25, Samuel Gougeon a écrit :
>>> Hello Stéphane,
>>>
>>> Le 17/01/2019 à 08:37, Stéphane Mottelet a écrit :
>>>> Hello Samuel,
>>>>
>>>> I have initially voted for this behavior (sparse([]) == ( 0,  0) 
>>>> zero sparse matrix ) but your remark on numerous occurences of 
>>>> "sparse([])" in scilab prevented to do so.
>>>
>>> Why? My remark aimed to bring the attention to existing occurrences 
>>> and to prevent merging the commit without updating them, not to 
>>> prevent updating them.
>>> Then these occurrences changed your opinion and vote, not mine.
>>>
>>> Best regards
>>> Samuel
>>
>> Please see comment #8:
>>
>> Anyway, *as bug #15758 is not related to sparse([]) being not 
>> sparse*, and considered the numerous side effects, I will restore 
>> sparse([]) == double empty matrix. *If you find necessary to have 
>> sparse([]) == sparse empty matrix, please file a bug/whish on BZ.*
>>
>
> Yes, and neither you -- that voted for it -- nor me did it.
> And finally we agree: keeping sparse([])==[] was your decision.
> Changing this could be done later if it proves to be better.
> For the time being, the situation is the following:
>
> *Scilab 6.0.1*:
> --> sparse([])
>  ans  =
>     []
>
> --> sparse([],[])
>  ans  =
> (  0,  0) zero sparse matrix
>
> --> sparse([],[],[0,2])
>  ans  =
>     []
>
> *Scilab 6.0.2-* after https://codereview.scilab.org/20492 :
> --> sparse([])      // unchanged
>  ans  =
>     []
>
> --> sparse([],[])   // unchanged
>  ans  =
> (  0,  0) zero sparse matrix
>
> --> sparse([],[],[0,2])  // *CHANGED*
>  ans  =
> (  0,  0) zero sparse matrix
>
> while i don't think that this last change is intentional.

it is. To me,

sparse([],[]) <=> sparse([],[],[0,0]) by getting dims implicitely 
defined in first two arguments (ij,v), so explicit size definition in 
sparse([],[],[2,0]) should give the same output (2x0 == empty matrix);

S.

> This is what Antoine is pointing to, in 
> https://codereview.scilab.org/20612.
>
> Samuel
>
>
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-- 
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

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