CPXXcallbackmakebranch and CPXcallbackmakebranch

The routine CPXXcallbackmakebranch/CPXcallbackmakebranch defines the branching constraints that define a branch from the current node in the MIP search tree, from the context CPX_CALLBACKCONTEXT_BRANCHING. The branch can include both variable bound changes and additional linear constraints.

int CPXXcallbackmakebranch( CPXCALLBACKCONTEXTptr context, CPXDIM varcnt, CPXDIM const * varind, char const * varlu, double const * varbd, CPXDIM rcnt, CPXNNZ nzcnt, double const * rhs, char const * sense, CPXNNZ const * rmatbeg, CPXDIM const * rmatind, double const * rmatval, double nodeest, CPXCNT * seqnum_p )

int CPXcallbackmakebranch( CPXCALLBACKCONTEXTptr context, int varcnt, int const * varind, char const * varlu, double const * varbd, int rcnt, int nzcnt, double const * rhs, char const * sense, int const * rmatbeg, int const * rmatind, double const * rmatval, double nodeest, int * seqnum_p )

Description

Warning: Your call of this function is valid only if the callback was invoked in the context CPX_CALLBACKCONTEXT_BRANCHING. In all other contexts, it returns an error.

Table 1. Values of varlu[i]
L	change the lower bound
U	change the upper bound
B	change both upper and lower bounds

Table 2. Values of sense[i]
L	less than or equal to constraint
E	equal to constraint
G	greater than or equal to constraint

Arguments

context: The callback context as passed into the callback function.
varcnt: An integer that specifies the number of bound changes that are specified in the arrays varind, varlu, and varbd.
varind: Together with varlu and varbd, this array defines the bound changes for the branch. The entry varind[i] is the index for the variable.
varlu: Together with varind and varbd, this array defines the bound changes for the branch. The entry varlu[i] is one of three possible values specifying which bound to change. Those values appear in Table 1.
varbd: Together with varind and varlu, this array defines the bound changes for the branch. The entry varbd[i] specifies the new value of the bound.
rcnt: An integer that specifies the number of constraints for the branch.
nzcnt: An integer that specifies the number of nonzero constraint coefficients for the branch. This specifies the length of the arrays rmatind and rmatval.
rhs: An array of length rcnt containing the righthand side term for each constraint for the branch.
sense: An array of length rcnt containing the sense of each constraint to be added for the branch. Possible values appear in Table 2.
rmatbeg: An array that with rmatbeg and rmatind defines the constraints for the branch.
rmatind: An array that with rmatbeg and rmatind defines the constraints for the branch.
rmatval: An array that with rmatbeg and rmatind defines the constraints for the branch. The format is similar to the format used to describe the constraint matrix in the routine CPXXaddrows/CPXaddrows. Every row must be stored in sequential locations in this array from positionrmatbeg[i] to rmatbeg[i+1]-1 (or from rmatbeg[i] to nzcnt-1 if i=rcnt-1). Each entry, rmatind[i], specifies the column index of the corresponding coefficient, rmatval[i]. All rows must be contiguous, and rmatbeg[0] must be 0.
nodeest: A double that specifies the value of the node estimate for the node to be created with this branch. The node estimate is used to select nodes from the branch-and-cut tree with certain values of the pararameter to control MIP node selection strategy (CPXPARAM_MIP_Strategy_NodeSelect).
seqnum_p: A pointer to an integer that, on return, will contain the unique identifier number that CPLEX has assigned to the node created from this branch.

Return

The routine returns 0 (zero) if successful and nonzero if an error occurs.