Re: [ublas] Sparse matrices can contain zeroes

Subject: Re: [ublas] Sparse matrices can contain zeroes
From: Alex Hagen-Zanker (ahh34_at_[hidden])
Date: 2011-02-18 12:40:55

On 18/02/2011 17:24, Thomas Klimpel wrote:
> Alex Hagen-Zanker wrote:
>>  From the documentation it seems that sparse matrices only contain
>> non-zero values and that iterators can be used to iterate over all
>> non-zero values.
>>
>> I found however that assigning the value 0 to an element puts it into
>> the matrix and causes iterators to iterate over it.
>>
>> Am I doing / seeing something wrong?
> I guess for sparse matrices, there are two types of zeros: structural zeros and ordinary zeros. If we are talking about the non-zero elements of a sparse matrix, we mean the structural non-zero elements, not the set of matrix elements whose values happen to be different from zero.
>
OK, thanks. My ordinary zeroes are structural zeroes and the other way 
round. It's good to understand that the mapped_matrix is not making that 
link for me.