CPXXaddcols and CPXaddcols

Description

The routine CPXXaddcols/CPXaddcols adds columns to a specified CPLEX problem object. This routine may be called any time after a problem object is created via CPXXcreateprob/CPXcreateprob.

The routine CPXXaddcols/CPXaddcols is very similar to the routine CPXXaddrows/CPXaddrows. The primary difference is that CPXXaddcols/CPXaddcols cannot add coefficients in rows that do not already exist (that is, in rows with index greater than the number returned by CPXXgetnumrows/CPXgetnumrows); whereas CPXXaddrows/CPXaddrows can add coefficients in columns with index greater than the value returned by CPXXgetnumcols/CPXgetnumcols, by the use of the ccnt argument. (See the discussion of the ccnt argument for CPXXaddrows/CPXaddrows.) Thus, CPXXaddcols/CPXaddcols has no variable ccnt and no array colname.

The routine CPXXnewrows/CPXnewrows can be used to add empty rows before adding new columns via CPXXaddcols/CPXaddcols.

The nonzero elements of every column must be stored in sequential locations in the array cmatval from position cmatbeg[i] to cmatbeg[i+1] (or from cmatbeg[i] to nzcnt-1 if i=ccnt-1). Each entry, cmatind[i], specifies the row number of the corresponding coefficient, cmatval[i]. Unlike CPXXcopylp/CPXcopylp, all columns must be contiguous, and cmatbeg[0] must be 0 (zero).

When you build or modify your problem with this routine, you can verify that the results are as you intended by calling CPXcheckaddcols during application development.

Arguments

env

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

lp

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

ccnt

An integer that specifies the number of new columns being added to the constraint matrix.

nzcnt

An integer that specifies the number of nonzero constraint coefficients to be added to the constraint matrix.

obj

An array of length ccnt containing the objective function coefficients of the new variables. May be NULL, in which case, the objective coefficients of the new columns are set to 0.0 (zero).

cmatbeg

Array that specifies the nonzero elements of the columns being added.

cmatind

Array that specifies the nonzero elements of the columns being added.

cmatval

Array that specifies the nonzero elements of the columns being added. The format is similar to the format used to specify the constraint matrix in the routine CPXXcopylp/CPXcopylp. (See description of matbeg, matcnt, matind, and matval in that routine).

lb

An array of length ccnt containing the lower bound on each of the new variables. Any lower bound that is set to a value less than or equal to that of the constant -CPX_INFBOUND is treated as negative infinity. CPX_INFBOUND is defined in the header file cpxconst.h. May be NULL, in which case the lower bounds of the new columns are set to 0.0 (zero).

ub

An array of length ccnt containing the upper bound on each of the new variables. Any upper bound that is set to a value greater than or equal to that of the constant CPX_INFBOUND is treated as infinity. CPX_INFBOUND is defined in the header file cpxconst.h. May be NULL, in which case the upper bounds of the new columns are set to CPX_INFBOUND (positive infinity).

colname

An array of length ccnt containing pointers to character strings that specify the names of the new variables added to the problem object. May be NULL, in which case the new columns are assigned default names if the columns already resident in the CPLEX problem object have names; otherwise, no names are associated with the variables. If column names are passed to CPXXaddcols/CPXaddcols but existing variables have no names assigned, default names are created for them.

Return

Example

status = CPXaddcols (env, lp, ccnt, nzcnt, obj, cmatbeg,
cmatind, cmatval, lb, ub, newcolname);