nnz() puede ser mayor que 2^31. canbiar a long

Freely Available Software for Linear Algebra
http://www.netlib.org/utk/people/JackDongarra/la-sw.html


- Test differente buffer sizes for pipes in Windows.
- Substructuring method for non symmetric matrices.
- Implement EqnSolver for sparse matrices with Saad's format.
- Use mkstemp instead of mktemp.


Implement
Y. Shapira
Parallelizable approximate solvers for recursions arising in preconditioning
Linear Algebra Applications. Vol. 274, pp. 211237
1998
