Tie breaking in the simplex method
• Tie for the entering basic variable
• If there is a tie (more than one variables have the same most negative or positive)
in determining the entering variable, choose any variable to be the entering one.
• Tie for the leaving basic variable – degeneracy
• If there is a tie in determining the leaving variable, choose any one to be the
leaving variable. In this case a zero will appear in RHS column; therefore, a “cycle”
will occur, this means that the value of the objective function will be the same for
several iterations.
• No leaving basic variable – unbounded Z
• When determining the leaving variable of any tableau, if there is no positive ratio
(all the entries in the pivot column are negative and zeroes), then the solution is
unbounded.
• Multiple optimal solutions
• If there is a zero coefficient in row 0 for one or more nonbasic variables in the last
tableau (optimal solution tableau), then there is a multiple optimal solution.