solves sparse linear systems in exact arithmetic

 Suitesparse is a collection of libraries for computations involving
 sparse matrices.
 .
 SPEX Left LU is a software package designed to exactly solve unsymmetric sparse
 linear systems, Ax = b, where A, b and x contain rational numbers. This
 package performs a left-looking, roundoff-error-free (REF) LU factorization
 PAQ = LDU, where L and U are integer, D is diagonal, and P and Q are row and
 column permutations, respectively. Note that the matrix D is never explicitly
 computed nor needed; thus this package uses only the matrices L and U.
 .
 This package relies on GNU GMP and MPRF for exact arithmetic computations.