/********************************************************
  Xpress-BCL Java Example Problems
  ================================

  file xbcutex.java
  `````````````````
  Simplified version of xbexpl1.java showing how
  to define cuts with BCL.

  (c) 2008 Fair Isaac Corporation
      author: S.Heipcke, 2005, rev. Dec. 2011
********************************************************/

import java.io.*;
import com.dashoptimization.*;

public class xbcutex {
    static final int NJ = 4;        /* Number of jobs */
    static final int NT = 10;       /* Time limit */

    /**** DATA ****/
    static final double[] DUR = {3,4,2,2};   /* Durations of jobs   */

    static XPRBvar[] start;         /* Start times of jobs  */
    static XPRBvar[][] delta;       /* Binaries for start times */
    static XPRBvar z;               /* Maximum completion time (makespan) */

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

    static class CutMgrCallback implements XPRScutMgrListener {
        public int XPRScutMgrEvent(XPRSprob oprob, Object data) {
            XPRBprob bprob;
            XPRBcut[] ca;
            int num,i;

            bprob = (XPRBprob)data;       /* Get the BCL problem */

            try  {
                bprob.beginCB(oprob);
                num = oprob.getIntAttrib(XPRS.NODES);
                if(num == 2) {                  /* Only generate cuts at node 2 */
                    ca = new XPRBcut[2];
                    ca[0] = bprob.newCut(start[1].add(2) .lEql(start[0]), 2);
                    ca[1] = bprob.newCut(start[2].mul(4) .add(start[3].mul(-5,3)) .lEql(-17), 2);
                    System.out.println("Adding constraints:");
                    for(i=0;i<2;i++) ca[i].print();
                    bprob.addCuts(ca);
                }
                bprob.endCB();
            }
            catch(XPRSprobException e) {
                System.out.println("Error  " + e.getCode() + ": " + e.getMessage());
            }
            return 0;                     /* Call this method once per node */
        }
    }

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

    static void jobsModel(XPRBprob p) {
        XPRBexpr le;
        int j,t;

        /****VARIABLES****/
        start = new XPRBvar[NJ];       /* Create start time variables */
        for(j=0;j<NJ;j++) start[j] = p.newVar("start");
        z = p.newVar("z",XPRB.PL,0,NT);  /* Declare the makespan variable */

        delta = new XPRBvar[NJ][NT];
        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), XPRB.BV);

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

        p.newCtr("Prec", start[0].add(DUR[0]).lEql(start[2]) );
        /* Precedence rel. between jobs */

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

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

        /****OBJECTIVE****/
        p.setObj(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 */

        /****OUTPUT****/
        p.print();                     /* Print out the problem definition */
    }

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

    static void jobsSolve(XPRBprob p) throws XPRSexception {
        int j,t,statmip;
        XPRSprob oprob;
        CutMgrCallback cb;

        oprob = p.getXPRSprob();        /* Get Optimizer problem */
        oprob.setIntControl(XPRS.HEUREMPHASIS, 0);
        oprob.setIntControl(XPRS.CUTSTRATEGY, 0);
        /* Switch automated cut generation off:
           otherwise this problem is solved in the
           first node of the MIP search tree */

        p.setCutMode(1);                /* Switch presolve off, enable cut manager */
        cb = new CutMgrCallback();
        oprob.addCutMgrListener(cb, p);

        p.setSense(XPRB.MINIM);
        p.mipOptimize("");              /* Solve the problem as MIP */
        statmip = p.getMIPStat();       /* Get the MIP problem status */

        if((statmip == XPRB.MIP_SOLUTION) || (statmip == XPRB.MIP_OPTIMAL))
            {             /* An integer solution has been found */
                System.out.println("Objective: "+ p.getObjVal());
                for(j=0;j<NJ;j++)
                    {                              /* Print the solution for all start times */
                        System.out.println(start[j].getName() + ": "+ start[j].getSol());
                        for(t=0;t<NT-DUR[j]+1;t++)
                            System.out.print(delta[j][t].getName() + ": "+ delta[j][t].getSol());
                        System.out.println();
                    }
            }
    }

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

    public static void main(String[] args) throws XPRSexception {
        try (XPRBprob p = new XPRBprob("Jobs"); /* Initialize BCL and create a new problem */
             XPRS xprs = new XPRS()) {           /* Initialize Xpress-Optimizer */

            jobsModel(p);                   /* Basic problem definition */

            jobsSolve(p);                  /* Solve and print solution */
        }
    }
}