/******************************************************** Xpress-BCL C# Example Problems ============================== file xbcutex.cs ``````````````` Simplified version of xbexpl1.cxx showing how to define cuts with BCL. (c) 2008-2024 Fair Isaac Corporation authors: S.Heipcke, D.Brett. ********************************************************/ using System; using System.Text; using System.IO; using Optimizer; using BCL; namespace Examples { public class TestUGCutex { const int NJ = 4; /* Number of jobs */ const int NT = 10; /* Time limit */ /**** DATA ****/ double[] DUR = {3,4,2,2}; /* Durations of jobs */ XPRBvar[] start = new XPRBvar[NJ]; /* Start times of jobs */ XPRBvar[,] delta = new XPRBvar[NJ,NT]; /* Binaries for start times */ XPRBvar z; /* Maximum completion time (makespan) */ XPRBprob p = new XPRBprob("Jobs"); /* Initialize BCL and a new problem */ /***********************************************************************/ public int usrcme(XPRSprob xprsp, object vd) { XPRBcut[] ca = new XPRBcut[2]; int num; int i=0; XPRBprob bprob = (XPRBprob)vd; bprob.beginCB(xprsp); /* In terms of an example, we add a few additional constraints (without any relation to the original problem) at the second node of the MIP search tree. These constraints/cuts are applied at this node and all its child nodes. */ num = xprsp.Nodes; if(num == 2) { ca[0] = bprob.newCut(start[1]+2 <= start[0], 2); ca[1] = bprob.newCut((4*start[2]) - (5,3*start[3]) <= -17, 2); System.Console.WriteLine("Adding constraints:"); for(i=0;i<2;i++) ca[i].print(); if(bprob.addCuts(ca,2) != 0) System.Console.WriteLine("Problem with adding cuts."); } bprob.endCB(); return 0; /* Call this function once per node */ } /*************************************************************************/ public void jobsModel() { XPRBexpr le; int j,t; /****VARIABLES****/ /* Create start time variables */ for(j=0;j<NJ;j++) start[j] = p.newVar("start");
            z = p.newVar("z", BCLconstant.XPRB_PL, 0, NT);  /* Declare the makespan variable */

            for(j=0;j<NJ;j++)              /* Declare binaries for each job  */
                for(t=0;t<(NT-DUR[j]+1);t++)
                    delta[j, t] = p.newVar("delta" + (j+1) + (t+1), BCLconstant.XPRB_BV);

            /****CONSTRAINTS****/
            for(j=0;j<NJ;j++)              /* Calculate maximal completion time */
                p.newCtr("Makespan", start[j]+DUR[j] <= z);

            p.newCtr("Prec", start[0]+DUR[0] <= start[2]);
            /* Precedence relation between jobs  */

            for(j=0;j<NJ;j++)              /* Linking start times and binaries  */
            {
                le= new XPRBexpr(0);
                for(t=0;t<(NT-DUR[j]+1);t++)  le += (t+1)*delta[j,t];
                p.newCtr("Link_" + (j+1), le == start[j]);
            }

            for(j=0;j<NJ;j++)              /* One unique start time for each job  */
            {
                le= new XPRBexpr(0);
                for(t=0;t<(NT-DUR[j]+1);t++)  le += delta[j,t];
                p.newCtr("One_" + (j+1), le == 1);
            }

            /****OBJECTIVE****/
            p.setObj(p.newCtr("OBJ", new XPRBexpr(z)));  /* Define and set objective function */

            /****BOUNDS****/
            for(j=0;j<NJ;j++) start[j].setUB(NT-DUR[j]+1);
            /* Upper bounds on start time variables */
        }

        /*************************************************************************/

        public void jobsSolve()
        {
            int j,t,statmip;
            CutmgrCallback del = new CutmgrCallback(usrcme);
            XPRSprob xprsp = p.getXPRSprob();

            xprsp.HeurEmphasis = 0;
            xprsp.CutStrategy = 0;

            /* Switch heuristics and cut generation off:
            otherwise this problem is solved in the
            first node of the MIP search tree */

            p.setCutMode(1);                /* Enable the cut mode */

            xprsp.AddCutmgrCallback(del, (object)p);

            p.setSense(BCLconstant.XPRB_MINIM);
            p.mipOptimize();                   /* Solve the problem as MIP */
            statmip = p.getMIPStat();       /* Get the MIP problem status */

            if ((statmip == BCLconstant.XPRB_MIP_SOLUTION) || (statmip == BCLconstant.XPRB_MIP_OPTIMAL))
            /* An integer solution has been found */
            {
                System.Console.WriteLine("Objective: " + p.getObjVal());
                for(j=0;j<NJ;j++)
                {                              /* Print the solution for all start times */
                    System.Console.WriteLine(start[j].getName() + ": " + start[j].getSol());
                    for(t=0;t<NT-DUR[j]+1;t++)
                        System.Console.Write(delta[j,t].getName() + ": " + delta[j,t].getSol() + " ");
                    System.Console.WriteLine();
                }
            }
        }

        /*************************************************************************/

        public static void Main()
        {
           XPRB.init();
           TestUGCutex TestInstance = new TestUGCutex();

            TestInstance.jobsModel();                   /* Basic problem definition */
            TestInstance.jobsSolve();                   /* Solve and print solution */

            return;
        }
    }
}