CPXcopystart

Description

The routine CPXcopystart() is used to provide starting information for use in a subsequent call to a simplex optimization routine (CPXlpopt() with CPX_PARAM_LPMETHOD or CPX_PARAM_QPMETHOD set to CPX_ALG_PRIMAL or CPX_ALG_DUAL, CPXdualopt(), CPXprimopt(), or CPXhybnetopt()). Starting information is not applicable when using the barrier optimizer or the mixed integer optimizer.

When a basis (parameters cstat and rstat) is installed for a linear problem and CPXlpopt() is used with CPX_PARAM_LPMETHOD set to CPX_ALG_AUTOMATIC, CPLEX will use the primal simplex algorithm if the basis is primal feasible and the dual simplex method otherwise.

Any of three different kinds of starting points can be provided: a starting basis (cstat, rstat), starting primal values (cprim, rprim), and starting dual values (cdual, rdual). Only a starting basis is applicable to a CPXhybnetopt() call, but for Dual Simplex and Primal Simplex any combination of these three types of information can be of use in providing a starting point. If no starting-point is provided, this routine returns an error; otherwise any resident starting information in the CPLEX problem object is freed and the new information is copied into it.

If you provide a starting basis, then both cstat and rstat must be specified. It is permissible to provide cprim with or without rprim, or rdual with or without cdual; arrays not being provided must be passed as NULL pointers.

The starting information is ignored by the optimizers if the CPX_PARAM_ADVIND parameter is off.

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

int CPXcopystart (CPXCENVptr env, CPXLPptr lp, const int *cstat, const int *rstat, const double *cprim, const double *rprim, const double *cdual, const double *rdual);

Arguments

The pointer to the CPLEX environment as returned by CPXopenCPLEX().

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

An array containing the basis status of the columns in the constraint matrix. The length of the array is equal to the number of columns in the CPLEX problem object.

Values for cstat[j]:

If this array is NULL, rstat must be NULL.

An array containing the basis status of the slack/surplus/artificial variable associated with each row in the constraint matrix. The array's length is equal to the number of rows in the LP problem. For rows other than ranged rows, the array element rstat[i] has the following meaning:

For ranged rows, the array element rstat[i] has the following meaning:

If this array is NULL, cstat must be NULL.

An array containing the initial primal values of the column variables. The length of the array must be no less than the number of columns in the CPLEX problem object. If this array is NULL, rprim must be NULL.

An array containing the initial primal values of the slack (row) variables. The length of the array must be no less than the number of rows in the CPLEX problem object. This array may be NULL.

An array containing the initial values of the reduced costs for the column variables. The length of the array must be no less than the number of columns in the CPLEX problem object. This array may be NULL.

An array containing the initial values of the dual variables for the rows.The length of the array must be no less than the number of rows in the CPLEX problem object. If this array is NULL, cdual must be NULL.

status = CPXcopystart (env, lp, cstat, rstat, cprim, rprim, cdual, rdual);