Simplex: The frequency with which the
basis will
be inverted. The basis is maintained in a factorized form and on most simplex iterations it is
incrementally updated to reflect the step just taken. This is considerably faster than computing the
full inverted matrix at each iteration, although after a number of iterations the basis becomes less
well-conditioned and it becomes necessary to compute the full inverted matrix. The value of
INVERTFREQ specifies the maximum number of iterations between full inversions.