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Purpose
Obtain a certificate of LP infeasibility.
Synopsis
int QSget_infeas_array (QSprob p, double *pi)
Arguments
p a handle to an initialized problem.
pi returns multipliers for a Farkas-like certificate of LP infeasibility; this should point to an array of length at least nrows, the number of rows in the problem.
Returns
A zero value if the function terminated correctly, and a non-zero value if an error occurred. Note that QSget_infeas_array will return an error unless either QSopt_primal reports infeasibility or QSopt_dual reports unboundedness.
Description

This function returns dual multipliers that can be used in a Farkas-like certificate of LP infeasibility. It can be used within an integer programming code to verify that an LP relaxation is really infeasible before pruning a branch-and-bound tree.

Example
/* p is an initialized QSprob, a handle to an existing LP problem.  */

int rval, nrows;
double *pi;

nrows = QSget_rowcount (p);
pi = (double *) malloc (nrows * sizeof (double));

rval = QSget_infeas_array (p, pi);
if (rval) {
    fprintf (stderr, 
            "Could not get certificate, error code %d\n", rval);
}

free (pi);
 
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Last Updated: November 2003