CPXgetcallbacknodeinfo

The routine CPXgetcallbacknodeinfo is called from within user-written callbacks during a MIP optimization and accesses information about nodes.

The primary purpose of this routine is to examine nodes in order to select one from which to proceed. In this case the wherefrom argument is CPX_CALLBACK_MIP_NODE, and a node with any nodeindex value can be queried. A secondary purpose of this routine is to obtain information about the current node. When the wherefrom argument is any one of the following values, only the current node can be queried.

CPX_CALLBACK_MIP_CUT
CPX_CALLBACK_MIP_INCUMBENT
CPX_CALLBACK_MIP_HEURISTIC
CPX_CALLBACK_MIP_SOLVE
CPX_CALLBACK_MIP_BRANCH

To query the current node, specify a nodeindex value of 0. Other values of the wherefrom argument are invalid for this routine. An invalid nodeindex value or wherefrom argument value will result in an error return value.

Note

The values returned for CPX_CALLBACK_INFO_NODE_SIINF and CPX_CALLBACK_INFO_NODE_NIINF for the current node are the values that applied to the node when it was stored and thus before the branch was solved. As a result, these values should not be used to assess the feasibility of the node.

This routine cannot retrieve information about nodes that have been moved to node files. For more information about node files, see the ILOG CPLEX User's Manual. If the argument nodeindex refers to a node in a node file, CPXgetnodecallbackinfo returns the value CPXERR_NODE_ON_DISK. Nodes still in memory have the lowest index numbers so a user can loop through the nodes until CPXgetcallbacknodeinfo returns an error, and then exit the loop.

Example

 status = CPXgetnodecallbackinfo(env,
                                 curlp,
                                 wherefrom,
                                 0,
                                 CPX_CALLBACK_INFO_NODE_NIINF,
                                 &numiinf);

Table 1: Information Requested for a User-Written Node Callback
Symbolic Constant	C Type	Meaning
`CPX_CALLBACK_INFO_NODE_SIINF`	`double`	sum of integer infeasibilities
`CPX_CALLBACK_INFO_NODE_NIINF`	`int`	number of integer infeasibilities
`CPX_CALLBACK_INFO_NODE_ESTIMATE`	`double`	estimated integer objective
`CPX_CALLBACK_INFO_NODE_DEPTH`	`int`	depth of node in branch & cut tree
`CPX_CALLBACK_INFO_NODE_OBJVAL`	`double`	objective value of LP subproblem
`CPX_CALLBACK_INFO_NODE_TYPE`	`int`	type of branch at this node; see Table 2
`CPX_CALLBACK_INFO_NODE_VAR`	`int`	for nodes of type `CPX_TYPE_VAR`, the branching variable for this node; for other types, -1 is returned
`CPX_CALLBACK_INFO_NODE_SOS`	`int`	for nodes of type `CPX_TYPE_SOS1` or `CPX_TYPE_SOS2` the number of the SOS used in branching; `-1` otherwise
`CPX_CALLBACK_INFO_NODE_SEQNUM`	`int`	sequence number of the node
`CPX_CALLBACK_INFO_NODE_NODENUM`	int	node index of the node (only available for `CPXgetcallbackseqinfo`)

Table 2: Branch Types Returned when whichinfo = CPX_CALLBACK_INFO_NODE_TYPE
Symbolic Constant	Value	Branch Type
`CPX_TYPE_VAR`	`'0'`	variable branch
`CPX_TYPE_SOS1`	`'1'`	SOS1 branch
`CPX_TYPE_SOS2`	`'2'`	SOS2 branch
`CPX_TYPE_USER`	`'X'`	user-defined
`CPX_TYPE_ANY`	`'A'`	multiple bound changes and/or constraints were used for branching

See also Advanced MIP Control Interface in the ILOG CPLEX User's Manual.

env	A pointer to the CPLEX environment, as returned by `CPXopenCPLEX`.
cbdata	The pointer passed to the user-written callback. This parameter must be the value of `cbdata` passed to the user-written callback.
wherefrom	An integer value indicating where the user-written callback was called from. This parameter must be the value of `wherefrom` passed to the user-written callback.
nodenum	The index of the node for which information is requested. Nodes are indexed from `0` (zero) to `(nodecount - 1)` where `nodecount` is obtained from the callback information function `CPXgetcallbackinfo`, with a `whichinfo` value of `CPX_CALLBACK_INFO_NODES_LEFT`.
whichinfo	An integer indicating which information is requested. Table 1 summarizes the possible values. Table 2 summarizes possible values returned when the type of information requested is branch type (that is, `whichinfo` = `CPX_CALLBACK_INFO_NODE_TYPE`).
result_p	A generic pointer to a variable of type double or int, representing the value returned by `whichinfo`. (The column “C Type” in Table 1 indicates the type of various values returned by `whichinfo`.)

CPXgetcallbacknodeinfo

Parameters:

Returns: