Re: [Bug-gsl] Documentation: gsl_spmatrix_alloc_nzmax does not necessarily initialize to all-zeros

[Patrick Alken]

Hello,

  Thanks for the report. I think the best fix is to check for nz == 0 in
gsl_spmatrix_get rather than setting p to 0 in the alloc function. I
made this change on the git, and also added a test for this in the
future. The issue should be fixed - let me know if you have any further
problems.

Thanks,
Patrick

On 01/19/2017 09:39 AM, Schmitz Manuel (LBC) wrote:
> The GSL documentation says in chapter 41.2 about function 
> "gsl_spmatrix_alloc_nzmax":
> "This function allocates a sparse matrix of size n1-by-n2 and initializes it 
> to all zeros."
>
> However, in the case of the CCS or the CRS storage format, the member "p" is 
> not initialized. Calling "gsl_spmatrix_get"  on a freshly allocated matrix 
> may yield a nonzero value, because its "p" member may contain offsets to an 
> unspecified location in memory.
> (Remark: The function gsl_spmatrix_get does not check against the "nz" 
> property of the matrix.)
>
> I have attached a modified version of the spmatrix.c file, which does 
> initialize the "p" vector when creating a matrix in CCS or CRS storage 
> format. But, I would prefer to adjust the documentation rather than the code, 
> because a zero-initialized matrix is not always necessary.
>
> Best regards
>
> i.A. Manuel Schmitz
>
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