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XPRBgetiis

XPRBgetiis

Purpose
Get the variables and constraints of an IIS.
Synopsis
int XPRBgetiis(XPRBprob prob, XPRBvar **arrvar, int *numv, XPRBctr **arrctr, int *numc, int numiis);
Arguments
prob 
Reference to a problem.
arrvar 
Reference to a table of BCL variables (may be NULL).
numv 
Reference to an integer that gets assigned the number of variables returned by the function (may be NULL).
arrctr 
Reference to a table of BCL constraints (may be NULL).
numc 
Reference to an integer that gets assigned the number of constraints returned by the function (may be NULL).
numiis 
Sequence number of the IIS or value 0 to access the IIS approximation.
Return value
0 if function executed successfully, 1 otherwise.
Example
The following prints out the variable and constraint names of the first IIS found for an infeasible LP problem. 
XPRBprob expl2;
XPRBctr *iisctr;
XPRBvar *iisvar;
int numv, numc;
expl2 = XPRBnewprob("example2");
   ...
XPRBlpoptimize(expl2, "");
if(XPRBgetlpstat(expl2)==XPRB_LP_INFEAS)
{
 XPRBgetiis(expl2, &iisvar, &numv, &iisctr, &numc, 1);
 printf("Variables: ");        /* Print all variables */
 for(i=0;i<numv;i++) printf("%s ", XPRBgetvarname(iisvar[i]));
 printf("\n");
 XPRBfreemem(iisvar);          /* Free the array of variables */
 printf("Constraints: ");      /* Print all constraints */
 for(i=0;i<numc;i++) printf("%s ", XPRBgetctrname(iisctr[i]));
 printf("\n");
 XPRBfreemem(iisctr);          /* Free the array of constraints */
}
Further information
1. This function returns the variables and constraints forming an IIS (irreducible infeasible set) in an infeasible LP problem. The number of independent IIS identified by Xpress Optimizer can be obtained with function XPRBgetnumiis.
2. The arrays of variables and constraints that are allocated by this function must be freed by the user's program by calls to XPRBfreemem.
3. The counting of IIS starts at 1. Value 0 for the argument numiis returns the information about the IIS approximation. Negative values or values larger than the number of IIS identified for the problem return 0 for the numbers of variables and constraints.
Related topics
XPRBgetnumiis, XPRBgetlpstat, XPRBgetmiis.

Parent Topic BCL C library functions

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