Originally posted by: AbdelhalimHiassat

Hello,

I have a strange problem. I am writing a branch callback in Callable Library, running c++ and CPLEX 12.5. Consider the following two lines:

status = CPXgetcallbacknodeub(env, cbdata, wherefrom, ubnode, 0 , orig_numcols-1);

status = CPXgetcallbacknodex (env, cbdata, wherefrom, solnode, 0, orig_numcols-1);

Now, this should return two arrays for the upper bounds and solution, respectively, in terms of the original (not the presolved) model.

Now, when I try to manually inspect a certain variable (via debugging), I found out that for this variable (index 2757 in my case), the upper bound is 0, while the (lp) solution is 1.

Is this possible?

Just to be sure, you explicitly set CPX_PARAM_MIPCBREDLP to 0 (the default is 1)?

Originally posted by: AbdelhalimHiassat

Yes.

How many threads are you using? Are the ubnode and solnode arrays local to the callback function or are these global arrays? Could it be that multiple threads access these arrays in parallel?

Originally posted by: AbdelhalimHiassat

Originally, I kept the number of threads as default (which I assume would use the maximum available; 4 threads in my machine). I tried to enforce using one thread only by this function:

status = CPXsetintparam (env, CPX_PARAM_THREADS, 1); .

This, however, didn't work. I still get the same problem: solution is greater than the upper bound for a certain variable.

Also, the arrays are local to the callback function. I even delete them after I'm done using them within the callback itself.