Re: Solving a large sparse system with a single dense row/column?


<goodchild.trevor@xxxxxxxxx> wrote in message
news:d7dbcccb-8ce8-49e5-a159-c4a7dec6357e@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Yes, I should have been more specific: my system has a dense column
*and* a dense row. I.e., the matrix looks somewhat like this:

/ \
| x x |
| x x |
| x x |
| x x |
| x x |
| x x |
| x x x x x x x |
\ /

(though in reality there are more off-diagonal entries and the system
may have blocks that are not symmetric).
Sorry for the confusion,


Based on your description, it seems each X is a [X], a block (or a
submatrix) not a coefficient. If, so, that is not the one I responded
previously. If each entry in your system is a coefficient and your system is
symmetric, variable bandwidth solver can take advantage of the sparsity. If
each entry is a block, that would be a different story. Renumbering deals
with unknowns, not blocks.

Based on your description, it seems your system has a dense block column and
dense block row. Are those offdiaginal blocks dense? If they are sparse
blocks, you can renumber your system to take advantage of sparse solver.


.

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