The routine CPXchgprobtype changes the current problem to a related problem. The problem types that can be used appear in the table.

A mixed integer problem (CPXPROB_MILP, CPXPROB_MIQP, or CPXPROB_MIQCP) can be changed to a fixed problem (CPXPROB_FIXEDMILP, CPXPROB_FIXEDMIQP), or CPXPROB_FIXEDMIQCP, where bounds on integer variables are fixed to the values attained in the integer solution. A mixed integer problem (or its related fixed type) can also be changed to a continuous problem (CPXPROB_LPCPXPROB_QP, or CPXPROB_QCP), which causes any existing ctype values to be permanently discarded from the problem object.

The original mixed integer problem can be recovered from the fixed problem. If the current problem type is CPXPROB_FIXEDMILP, CPXPROB_FIXEDMIQP, or CPXPROB_FIXEDMIQCP, any calls to problem modification routines fail. To modify the problem object, the problem type should be changed to CPXPROB_MILP, CPXPROB_MIQP, or CPXPROB_MIQCP.

Changing a problem from a continuous type to a mixed integer type causes a ctype array to be created such that all variables are considered continuous. A problem of type CPXPROB_MILP, CPXPROB_MIQP, or CPXPROB_MIQCP can be solved only by the routine CPXmipopt, even if all of its variables are continuous.

A quadratic problem (CPXPROB_QP, CPXPROB_MIQP, CPXPROB_QCP, or CPXPROB_MIQCP) can be changed to a linear program (CPXPROB_LP), causing any existing quadratic information to be permanently discarded from the problem object. Changing a problem from a linear program (CPXPROB_LP or CPXPROB_MILP) to a quadratic program (CPXPROB_QP or CPXPROB_MIQP) causes an empty quadratic matrix to be created such that the problem is quadratic with the matrix Q = 0.

Example

 status = CPXchgprobtype (env, lp, CPXPROB_MILP);