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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.