The saving feature of such problems is that it is very common for almost all the entries in the matrix to be zero. Matrices in which the large majority of elements are zero are called sparse matrices....

The saving feature of such problems is that it is very common for almost all the entries in the matrix to be zero. Matrices in which the large majority of elements are zero are called sparse matrices. Unless there is special structure to the equations, elimination will quickly destroy the sparseness.