[ublas] tridiagonal_matrix

From: dariomt_at_[hidden]
Date: 2008-01-15 04:00:36

I am trying to implement a tridiagonal_matrix (
http://en.wikipedia.org/wiki/Tridiagonal_matrix)
It is just a special case for a banded_matrix, where there are only one
diagonal above and under the main diagonal.

That is, a tridiagonal_matrix<T>(m, n) is functionally equivalent to a
banded_matrix<T>(m,n,1,1) (I probably want to make it square but that is
another subject)

I'd like to take advantage of very useful compile time info:
1) all elements outside the diagonals are zero
2) there are only three (3 compile time fixed!) diagonals

e.g

matrix<double> x;
tridiagonal_matrix<double> y;
matrix<double> z1 = prod(x,y);
matrix<double> z2 = x + y;

Both prod and operator+ should know that all values of y outside the three
diagonals are zero, to save many operations respect a (dense) matrix

Is this possible with ublas? How is this done?
TIA