Posted by Dave Becker on July 20, 1997 at 21:54:12:
In the lanz.f package, symmetric sparse matrices are
packed according to diagonal elements, then off-diagonal elements
with accompanying lists of row and columns pointers.
I don't understand the definition of row pointers.
For an nxn symmetric matrix, the code expects n diagonal
elements, n+1 row pointers, and m column pointers.
For the following "sparse" matrix then,
| 1. 7.4 0. 0. 2.2 |
| 2. 0. 0.2 3.0 |
| 4. 7.1 0. |
| sym .3 .7 |
| 1.3 |
the n diagonals would be
1.
2.
4.
.3
1.3
the 6 off-diagonal elements:
7.4
2.2
0.2
3.0
7.1
0.7
the 6 column pointers would be
2
5
4
5
4
5
But what are the row pointers? It seems like there would
be only n-1 of them.