Originally posted by: albaska

Hi,

I am trying to get the node id by the following command in three different callbacks, (solve, branch and node callback).

status = CPXgetcallbacknodeinfo(env, cbdata, wherefrom, 0,
                                  CPX_CALLBACK_INFO_NODE_SEQNUM, &nodeid);
  

The node id I get in solve and branch callbacks are always the same, but sometimes node callback returns a different number than the other callbacks. Can someone explain why this is happening? Thank you.

In the branch and solve callbacks, node number 0 refers to the current node.

In the node callback node number 0 refers to the next node to be selected. Maybe this can explain?

Originally posted by: albaska

That could be the reason for that. I also have another question, is it possible to get the parent's nodeid of the current node in Cplex? Thank you

No, that information is not available. However, you can easily track this yourself from a branch callback.

In the branch callback store the current node's seqnum, then call CPXbranchasCPLEX() and pass (void *)seqnum as user data for each new node. Then, when a node is processed you can call CPXgetcallbacknodeinfo(CPX_CALLBACK_INFO_NODE_USERHANDLE), cast the obtained void* back to CPXCNT and you have the sequence number of the parent node.

Originally posted by: albaska

I did this like below, but I always get 0 as parented in each node

in the branch callback:

  //ASSIGN THE CURRENT NODE ID TO THE CHILD

  int nodeid;
  status = CPXgetcallbacknodeinfo(env, cbdata, wherefrom, 0,
                                  CPX_CALLBACK_INFO_NODE_SEQNUM, &nodeid);

  status = CPXbranchcallbackbranchbds(env, cbdata, wherefrom, 1, &bestj, varlu,
                                      varbd, objval, (void *)nodeid, &seqnum1);  
  status = CPXbranchcallbackbranchbds(env, cbdata, wherefrom, 1, &bestj, varlu,
                                      varbd, objval, (void *)nodeid, &seqnum2);

Then again in the branch callback to get the parent nodeid:

  void * data= NULL;
  CPXINT parentid;
  status = CPXgetcallbacknodeinfo(env, cbdata, wherefrom, 0, 
              CPX_CALLBACK_INFO_NODE_USERHANDLE, &data);

  parentid = (CPXINT)(data);

  printf("parent node id is = %d\n",parentid);
  

do you have any suggestions? why parentid is always 0?

Note that the parent id of the first node (the root node) will always be 0 since the node data for the root data is NULL. Other than that, the parent ids should be different from zero. This callback implementation

static int
branchcallback(CPXCENVptr env, void *cbdata,
               int wherefrom, void *cbhandle, int brtype, CPXDIM brset,
               int nodecnt, CPXDIM bdcnt,
               const CPXDIM *nodebeg, const CPXDIM *xindex, const char *lu,
               const double *bd, const double *nodeest, int *useraction_p)

{
   int num, me;
   CPXCNT seqno;
   void *parent;
   int status;

   (void)cbhandle; (void)brtype; (void)brset; (void)bdcnt; (void)nodebeg;
   (void)xindex;   (void)lu;     (void)bd;    (void)nodeest;

   CPXXgetcallbacknodeinfo(env, cbdata, wherefrom, 0, 
                           CPX_CALLBACK_INFO_NODE_USERHANDLE, &parent);

   CPXXgetcallbacknodeinfo(env, cbdata, wherefrom, 0,
                           CPX_CALLBACK_INFO_NODE_SEQNUM, &me);

   printf("Branch callback on %d (parent %d)\n", me, (int)parent);

   for (num = 0; num < nodecnt; ++num)
      CPXXbranchcallbackbranchasCPLEX(env, cbdata, wherefrom,
                                      num, (void *)me, &seqno);
   *useraction_p = CPX_CALLBACK_SET;

   return 0;
}

produces the following output for me, which looks reasonable:

Branch callback on 0 (parent 0)
Branch callback on 2 (parent 0)
Branch callback on 3 (parent 2)
Branch callback on 5 (parent 3)
Branch callback on 7 (parent 5)
Branch callback on 9 (parent 7)
Branch callback on 11 (parent 9)
...

Originally posted by: albaska

Thank you. it is what I want