[ublas] quick survey: use of matrix-iterator duality

From: Gunter Winkler (guwi17_at_[hidden])
Date: 2006-07-06 04:38:49

Hello,

Do you use the duality feature of ublas' matrix iterators? 

That means create an iterator1, advance a few rows, create an iterator2 for 
the current row, advance some columns, create an iterator1, advance to 
another row:
matrix<double> A(n,n);
const_iterator1 it1 = A.begin1();
++it1;
const_iterator2 it2 = it1.begin();
++it2;
const_iterator1 it1a = it2.begin();
...

This feature is a major cause of the complexity of ublas' matrix iterators and 
the (strange & still undocumented) find{1,2}(...) functions.

I wonder if anyone really _needs_ this behavior. For dense matrices one could 
easily use indices and for sparse matrices one should never iterate 
orthogonal to the storage layout.

mfg
Gunter

PS: You may answer privately - I collect all votes ;-)