Re[2]: [Help-glpk] Speeding up GLPK

[Andrew Makhorin]

>I seem to remember reading that
>degeneracy and approximate arithmetic could make this tricky.
>Recomputation after tightening constraints might result in a basis
>that is neither dual nor primal feasible.
>Similarly for relaxing constraints.
>
>Is this still current information?
>Was it ever?
>
>As I handle a lot of M01LPs, this is likely to be significant to me.

If the dual simplex is enabled but the current basis is not dual
feasible, lpx_simplex automatically switches to the primal simplex.
This is used in the b&b solver and works fine for most instances.