Re: questions on ublas ?

From: jhrwalter (walter_at_[hidden])
Date: 2001-12-07 02:44:16

--- In boost_at_y..., Toon Knapen <toon.knapen_at_s...> wrote:
> jhrwalter wrote:
> 
> >>Does the sparse matrix also support COO (coordinate) and 
> >>most important CSC (compressed sparse row or Harwell-Boeing) 
> >>format ?
> > 
> > No. Our base containers vector, matrix, sparse_vector and 
> > sparse_matrix were designed to use std::vector and std::map as 
> > storage and prove interoperability. CRS and CCS storage formats 
have 
> > to be implemented. With regard to COO I'm unsure.
> > 
> 
> I've been looking at the code to see how COO and CSC could be added.
> 
> As for the COO, you are right that it is not necessary. The current 
> compressed_array could be used. 
 
Hm. I'll have to think about that.
 
> Most important though is that we prefer 
> to first construct the structure of the matrix and later fill in 
the 
> values. The speedup by constructing the structure first exactly 
comes 
> from that the internal array do not need to be sorted the whole 
time. 
> Where you sort the compressed_array now the whole time, I would 
like to 
> delay this sorting. This way it's more efficient.

compressed_array has a range insert member. Doesn't it suffice?
 
> After having built up the structure, the matrix would also need a 
> constructor that takes the structure as an argument (not only as a 
> template argument).
> 
> An option would be to add some members to work in non-sorted mode. 
For 
> instance a member function add_nnz(size_type, size_type) or just 
> add_nnz(size_type) that would add the entry but not force that 
data_ 
> would be sorted as a post-condition. When the structure is used to 
> construct another structure (like CSC) or used within a matrix 
> constructor, the sort would be triggered. This sort can also be 
> triggered by any call to any of  the other member functions of the 
> object but this might be inefficient.
 
Sorry, you've lost me. Are you talking about extending/changing 
existing sparse matrix formats or about new CRS and CCS formats here?
 
Regards
 
Joerg