CPXgetcallbacknodeinfo

Usage

Mixed Integer Users Only

Description

The routine CPXgetcallbacknodeinfo() is called from within user-written callbacks during a MIP optimization and accesses information about nodes. When the wherefrom argument is CPX_CALLBACK_MIP_NODE, a node with any nodeindex value can be queried. When the wherefrom argument is any one of CPX_CALLBACK_MIP_CUT, CPX_CALLBACK_MIP_INCUMBENT, CPX_CALLBACK_MIP_HEURISTIC, or CPX_CALLBACK_MIP_BRANCH, only the current node can be queried. This is done by specifying 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.

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.

Return Value

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

The return value CPXERR_NODE_ON_DISK indicates an attempt to access a node currently located in a node file on disk.

Synopsis 

  int CPXgetcallbacknodeinfo (CPXCENVptr env,
                              void *cbdata,
                              int wherefrom,
                              int nodeindex,
                              int whichinfo,
                              void *result_p);

Arguments

CPXCENVptr env

The pointer to the ILOG CPLEX environment, as returned by one of the CPXopenCPLEX routines.

void *cbdata

The pointer passed to the user-written callback. This parameter must be the value of cbdata passed to the user-written callback.

int 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.

int nodeindex

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.

int whichinfo

An integer indicating which information is requested. Table 1 summarizes possible values.

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 SOS-type branches, the rightmost variable in left subset 
CPX_CALLBACK_INFO_NODE_SOS 
int 
the number of the SOS used in branching; -1 if none used 
CPX_CALLBACK_INFO_NODE_SEQNUM 
int 
sequence number of the node 
CPX_CALLBACK_INFO_NODE_NODENUM 
int 
node index of the node 

Table 2 summarizes possible values returned when the type of information requested is branch type (that is, whichinfo = CPX_CALLBACK_INFO_NODE_TYPE).

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 

void *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.)

Example 

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

See Also

CPXgetcallbackinfo() (ILOG CPLEX Reference Manual), CPXgetcallbackseqinfo(), Advanced MIP Control Interface
Copyright © 2002 ILOG
http://www.ilog.com
 
 
 
 
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