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From: Sorkin Dmitri (dsorkin_at_[hidden])
Date: 2005-03-23 06:34:29

On Tue, 22 Mar 2005, Paul C. Leopardi wrote:
> Is it possible/valid to have a compressed matrix where the index1 array is
> complete and yet there are rows (or columns depending on type of compressed
> matrix) which contain no non-zeros? A simple example would be the zero
> matrix. Is is possible/valid to have a compressed matrix with no non-zeros
> and yet a complete index1 array? If not, wouldn't this badly break the
> expected linear algebra semantics of compressed matrices, eg. you would need
> to force some of the non-zeros to have the value zero?

   In "standard" CSR/CSC (compressed sparse column/rows) format it is
   Lets talk about CSC :
If you have an empty column, then a pointer to beginning to 'this' column
points to the same location as pointer to 'next' column.So you
easily detect empty column, by equality comparison of pointers in the
"index2" array.