Changes 4.13:

        A tentative implementation of the "exact" simplex method based
        on bignum (rational) arithmetic was included in the package.

        On API level this new feature is available through the routine
        lpx_exact, which is similar to the routine lpx_simplex.

        In the solver glpsol this feature is available through two new
        command-line options: --exact and --xcheck. If the '--exact'
        option is specified, glpsol solves LP instance using the exact
        simplex method; in case of MIP it is used to obtain optimal
        solution of LP relaxation. If the --xcheck option is specified,
        LP instance (or LP relaxation) is solved using the standard
        (floating-point) simplex method, however, then glpsol calls the
        exact simplex routine to make sure that the final LP basis is
        exactly optimal, and if it is not, to perform some additional
        simplex iterations in exact arithmetic.

Changes 4.12:
        A tentative implementation of some simplex method routines
        based on exact (bignum) arithmetic was included in the package.
        Currently these routines provide computing LU-factorization of
        the basis matrix and computing components of basic solution.

        These routines were used to implement a routine, which checks
        primal and dual feasibility of basic solution exactly, i.e. in
        rational numbers, without round-off errors. In glpsol this
        feature is available through the command-line option --xcheck.

        GLPK has its own low-level routines implementing operations on
        integer and rational numbers that makes it independent on other
        software packages. However, to attain a much better performance
        it is highly recommended to install (before configuring GLPK)
        the GNU Multiple Precision Arithmetic Library (GMP). Using GMP
        makes computations 100-200 times faster.

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