/******************************************************** Xpress-BCL Java Example Problems ================================ file xbcontr1.java `````````````````` Contract allocation example. Combining BCL problem input with problem solving in Xpress-Optimizer. (c) 2008-2023 Fair Isaac Corporation author: S.Heipcke, 2005, rev. Dec. 2011 ********************************************************/ import java.io.*; import com.dashoptimization.*; public class xbcontr1 { 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 */ /***********************************************************************/ public static void main(String[] args) throws XPRSexception, XPRSprobException { int d, c, i, stat, ncol, len; double [] sol; double val; java.lang.String [] names; XPRSprob op; XPRBexpr l1,l2,lobj; XPRBvar[][] x; /* Variables indicating whether a project is chosen */ XPRBvar[][] y; /* Quantities allocated to contractors */ try (XPRBprob p = new XPRBprob("Contract1"); /* Initialize BCL and create a new problem in 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****/
            p.loadMat();                    /* Load the matrix explicitly */
            op = p.getXPRSprob();           /* Retrieve the Optimizer problem */
            op.mipOptimize("");             /* Solve the MIP problem */

            stat = op.getIntAttrib(XPRS.MIPSTATUS);
            /* Get the global (MIP) status */
            if((stat==XPRS.MIP_SOLUTION) || (stat==XPRS.MIP_OPTIMAL))
                {                               /* Test whether an integer sol. was found */
                    val=op.getDblAttrib(XPRS.MIPOBJVAL);
                    System.out.println("Objective: " + val);

                    ncol=op.getIntAttrib(XPRS.COLS);
                    sol = new double[ncol];
                    op.getMipSol(sol);              /* Get the primal solution values */
                    names = new java.lang.String[ncol];
                    op.getNames(XPRS.NAMES_COLUMN, names, 0, ncol-1);  /* Get the variable names */

                    for(i=0; i<ncol; i++)          /* Print out the solution */
                        if(sol[i]!=0)
                            System.out.print(names[i] + ": " + sol[i] + ", ");
                    System.out.println();
                }

        }
    }
}