Contract - Semi-continuous variables, predefined constraint functions, combine BCL with Xpress Optimizer

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

  file xbcontr.java
  `````````````````
  Contract allocation example.

  (c) 2008 Fair Isaac Corporation
      author: S.Heipcke, Jan. 2000, rev. Mar. 2011
********************************************************/

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

public class xbcontr
{
 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 IOException
 {
  int d,c;
  XPRB bcl;
  XPRBprob p;
  XPRBexpr l1,l2,lobj;
  XPRBvar[][] x;                  /* Variables indicating whether a project 
                                     is chosen */
  XPRBvar[][] y;                  /* Quantities allocated to contractors */

  bcl = new XPRB();               /* Initialize BCL */
  p = bcl.newProb("Contract");    /* Create a new problem in BCL */
 
/**** 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.exportProb(XPRB.MPS,"Contract");   /* Output the matrix in MPS format */
  p.setSense(XPRB.MINIM);         /* Choose the sense of the optimization */   
  p.mipOptimize("");              /* Solve the MIP-problem */

  if((p.getMIPStat()==XPRB.MIP_SOLUTION) || (p.getMIPStat()==XPRB.MIP_OPTIMAL)) 
                                  /* Test whether an integer sol. was found */
  {              
   System.out.println("Objective: " + p.getObjVal()); /* Get objective value */
   for(d=0;d<District;d++)        /* Print the solution values */
   {
    for(c=0;c<Contract;c++)
     if(x[d][c].getSol()>0)
      System.out.print(y[d][c].getName() + ":" + y[d][c].getSol() + ", ");
    System.out.println();
   }
  } 
 }
}