/******************************************************** Xpress-BCL Java Example Problems ================================ file xbcontr2.java `````````````````` Contract allocation example. Combining BCL problem input with problem solving and callbacks in Xpress-Optimizer. (c) 2008 Fair Isaac Corporation author: S.Heipcke, 2005, rev. Dec. 2011 ********************************************************/ import java.io.*; import com.dashoptimization.*; public class xbcontr2 { static final int District = 6; /* Number of districts */ static final int Contract = 10; /* Number of contracts */ /**** DATA ****/ static final int[] OUTPUT = {50, 40, 10, 20, 70, 50}; /* Max. output per district */ static final int[] COST = {50, 20, 25, 30, 45, 40}; /* Cost per district */ static final int[] VOLUME = {20, 10, 30, 15, 20, 30, 10, 50, 10, 20}; /* Volume of contracts */ /***********************************************************************/ static class IntSolCallback implements XPRSintSolListener { public void XPRSintSolEvent(XPRSprob oprob, Object data) { int num, d, c; XPRBprob bprob; XPRBvar y; try { bprob = (XPRBprob)data; bprob.beginCB(oprob); num = oprob.getIntAttrib(XPRS.MIPSOLS); /* Get number of the solution */ bprob.sync(XPRB.XPRS_SOL); /* Update BCL solution values */ System.out.println("Solution " + num + ": Objective value: " + bprob.getObjVal()); for(d=0;d<District;d++) for(c=0;c<Contract;c++) y=bprob.getVarByName("q_d"+ +="_c">-1) && (y.getSol() != 0))
                            System.out.println(y.getName() + ": " + y.getSol());
                    }
                bprob.endCB();
            }
            catch(XPRSprobException e) {
                System.out.println("Error " + e.getCode() + ": " + e.getMessage());
            }
        }
    }

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

    public static void main(String[] args) throws XPRSexception {
        int d, c, i, stat, ncol, len;
        double [] sol;
        double val;
        java.lang.String [] names;
        XPRSprob op;
        IntSolCallback cb;
        XPRBexpr l1,l2,lobj;
        XPRBvar[][] x;                  /* Variables indicating whether a project
                                           is chosen */
        XPRBvar[][] y;                  /* Quantities allocated to contractors */

        try (XPRBprob p = new XPRBprob("Contract2"); /* Initialize BCL and create a new problem BCL */
             XPRS xprs = new XPRS()) {               /* Initialize Xpress-Optimizer */

            /**** VARIABLES ****/
            x = new XPRBvar[District][Contract];
            y = new XPRBvar[District][Contract];
            for(d=0;d<District;d++)
                for(c=0;c<Contract;c++) {
                    x[d][c] = p.newVar("x_d"+ (d+1) +"_c" +(c+1), XPRB.BV);
                    y[d][c] = p.newVar("q_d"+ (d+1) +"_c" +(c+1), XPRB.SC, 0, OUTPUT[d]);
                    y[d][c].setLim(5);
                }

            /****OBJECTIVE****/
            lobj = new XPRBexpr();
            for(d=0;d<District;d++)
                for(c=0;c<Contract;c++)
                    lobj.add(y[d][c].mul(COST[d]));

            p.setObj(lobj);                  /* Set the objective function */

            /**** CONSTRAINTS ****/
            for(c=0;c<Contract;c++) {
                l1 = new XPRBexpr();
                l2 = new XPRBexpr();
                for(d=0;d<District;d++) {
                    l1.add(y[d][c]);
                    l2.add(x[d][c]);
                }
                p.newCtr("Size", l1.gEql(VOLUME[c]));  /* "Size": cover the req. volume */
                p.newCtr("Min", l2.gEql(2) );  /* "Min": at least 2 districts / contract */
            }

            for(d=0;d<District;d++) {          /* Do not exceed max. output  */
                l1 = new XPRBexpr();
                for(c=0;c<Contract;c++)
                    l1.add(y[d][c]);
                p.newCtr("Output", l1.lEql(OUTPUT[d]) );
            }

            for(d=0;d<District;d++)         /* If a contract is allocated to a district,
                                               then at least 1 unit is allocated to it */
                for(c=0;c<Contract;c++)
                    p.newCtr("XY", x[d][c].lEql(y[d][c]) );

            /****SOLVING + OUTPUT****/
            cb = new IntSolCallback();
            p.getXPRSprob().addIntSolListener(cb,p);
            /* Define an integer solution callback */
            p.mipOptimize("");              /* Solve the MIP problem */

        }
    }
}