CPXgetiis

The routine CPXgetiis is used to examine the IIS for an infeasible LP problem. The IIS must already have been computed by a call to CPXfindiis or CPXiiswrite. On successful completion, the CPXgetiis arguments return information about the IIS that can be used to diagnose the cause of infeasibility. The number of rows and bound constraints in the IIS, as well as the indices of the IIS members, are returned.

Table 1: Values of iisstat_p
1	`CPXIIS_COMPLETE`	IIS found
2	`CPXIIS_PARTIAL`	Time limit exceeded, partial IIS found

Table 2: Values of elements of rowbdstat
`0`	`CPXIIS_AT_LOWER`	Row is at lower bound
`1`	`CPXIIS_FIXED`	Row is fixed
`2`	`CPXIIS_AT_UPPER`	Row is at upper bound

Table 3: Values of elements of colbdstat (status of column bounds)
`0`	`CPXIIS_AT_LOWER`	Column is at lower bound
`1`	`CPXIIS_FIXED`	Column is fixed
`2`	`CPXIIS_AT_UPPER`	Column is at upper bound

Example

 status = CPXgetiis (env, lp, &iisstat, rowind, rowbdstat,
 	                   &iisnumrows, colind, colbdstat,
                     &iisnumcols);

A pointer to the CPLEX environment as returned by the CPXopenCPLEX routine.

A pointer to a CPLEX problem object as returned by CPXcreateprob.

A pointer to an integer to contain the result of the IIS algorithm. The specific values that *iisstat_p can take and their meanings appear in Table 1.

An array to contain the indices of the rows in the IIS. The length of the array must be at least as large as the number of rows in the IIS.

An array that identifies the right-hand side value for each row in the IIS that is causing the infeasibility. Possible values appear in Table 2. The length of the array must be at least as large as the number of rows in the IIS. This information is needed only for ranged rows. For all other row senses, the value is uniquely determined by the sense.

A pointer to an integer to contain the number of rows in the IIS.

An array to contain the indices of the columns in the IIS. The length of the array must be at least as large as the number of columns in the IIS.

An array that identifies the bound for each column in the IIS that is causing the infeasibility. Possible values appear in Table 3. The length of the array must be at least as large as the number of columns in the IIS.

A pointer to an integer to contain the number of columns in the IIS.

The routine returns zero on success and nonzero if an error occurs.

CPXgetiis

Parameters:

Returns:

env	A pointer to the CPLEX environment as returned by the `CPXopenCPLEX` routine.
lp	A pointer to a CPLEX problem object as returned by `CPXcreateprob`.
iisstat_p	A pointer to an integer to contain the result of the IIS algorithm. The specific values that `*iisstat_p` can take and their meanings appear in Table 1.
rowind	An array to contain the indices of the rows in the IIS. The length of the array must be at least as large as the number of rows in the IIS.
rowbdstat	An array that identifies the right-hand side value for each row in the IIS that is causing the infeasibility. Possible values appear in Table 2. The length of the array must be at least as large as the number of rows in the IIS. This information is needed only for ranged rows. For all other row senses, the value is uniquely determined by the sense.
iisnumrows_p	A pointer to an integer to contain the number of rows in the IIS.
colind	An array to contain the indices of the columns in the IIS. The length of the array must be at least as large as the number of columns in the IIS.
colbdstat	An array that identifies the bound for each column in the IIS that is causing the infeasibility. Possible values appear in Table 3. The length of the array must be at least as large as the number of columns in the IIS.
iisnumcols_p	A pointer to an integer to contain the number of columns in the IIS.