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

[Samuel Gougeon]

Le 22/01/2019 à 18:06, Stéphane Mottelet a écrit :
> Le 22/01/2019 à 17:58, Samuel Gougeon a écrit :
>> Le 22/01/2019 à 17:56, Samuel Gougeon a écrit :
>>> Le 22/01/2019 à 17:40, Stéphane Mottelet a écrit :
>>>> 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
>>>>
>>>
>>> Yes
>>>
>>>> (2x0 == empty matrix);
>>>>
>>>
>>> No. Since both other syntaxes yielded [], [] should be returned. 
>>> What would make a consistent answer for *all* empty inputs.
>>
>> I mean: Changing
>>
>> --> sparse([],[])
>>  ans  =
>> (  0,  0) zero sparse matrix
>>
>> into
>>
>> --> sparse([],[])
>>  ans  =
>>    []
>
> I do not agree. I will prepare a patch with sparse([]) == (0,0) zero 
> sparse matrix for master and this time I will track all possible 
> glitches. Every output of sparse(...), whatever the arguments, should 
> be sparse, even if empty.
>

This was the missing intention.
Thanks

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