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Delivery - Data input from file; infeasibility analysis

Description
A simple supply and demand network example showing data input from file and the use of "views": incremental definition of arrays of variables. Also uses constraint templates with the arrays of variables.

A second version of this model (file xbdlvriis) has modified data making the problem infeasible. This example shows how to analyze infeasibility with the help of IIS (irreducible infeasible sets), it retrieves the IIS and prints out their contents.

It is possible to retrieve more detailed information on the IIS, such as isolation rows or bounds, using Xpress Optimizer functions (file xbdlvriis2iso) or to use the infeasibility repair functionality of the Optimizer (file xbdlvriis2rep) with models defined in BCL.

xbdelvrjava.zip[download all files]

Source Files

Data Files





xbdelvr.java

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

  file xbdelvr.java
  `````````````````
  Transportation problem.

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

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

public class xbdelvr
{
 static final int NSupp = 10;     /* Number of suppliers */
 static final int NCust = 7;      /* Number of customers */
 static final int MaxArcs = 100;  /* Max. num. of non-zero cost values */

 static final String VANFILE = System.getProperty("XPRBDATA") + 
   "/delivery/ifvan.dat";
 static final String COSTFILE = System.getProperty("XPRBDATA") + 
   "/delivery/cost.dat";

/****DATA****/
/* Supplier:                    London  Luton  B'ham Bristl  Derby Stckpt */
 static final double SUPPLY[] = {140.0, 600.0,  50.0,  10.0, 400.0, 200.0,  
/* Supplier: York  Derby Soton Scnthp */
             20.0, 90.0,  30.0,  12.0};
/* Customer:                    London Livpol Doncst   York   Hull Manchr */
 static final double DEMAND[] = {123.3,  56.4,  17.1, 192.8, 310.0,  47.0, 
/* Customer:  Shffld */    
              86.0};

 static double[][] COST;          /* Cost per supplier-customer pair */
 static double[][] IFVAN;         /* Non-zero if route uses vans instead 
                                     of lorries */
 static final double VANCAP=40.0; /* Capacity on routes that use vans */

 static XPRB bcl;
 static XPRBprob p;

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

 static void modDelivery() throws IOException
 {
  XPRBexpr lobj, lc;
  int s,c;
  XPRBvar[][] x;
 
  bcl = new XPRB();               /* Initialize BCL */
  p = bcl.newProb("Delivery");    /* Create a new problem in BCL */

/****VARIABLES****/
  x = new XPRBvar[NSupp][NCust];
  for(s=0;s<NSupp;s++)
   for(c=0; c<NCust; c++)
    x[s][c] = p.newVar("x_s" + s);
     
/****OBJECTIVE****/
  lobj = new XPRBexpr();
  for(s=0;s<NSupp;s++)            /* Objective: Minimize total cost */
   for(c=0; c<NCust; c++)
    lobj.add(x[s][c].mul(COST[s][c]));
  p.setObj(lobj); /* Set objective function */ 

/****CONSTRAINTS****/  
  for(c=0; c<NCust; c++)          /* Satisfy demand of each customer */
  {
   lc = new XPRBexpr();
   for(s=0;s<NSupp;s++)  lc.add(x[s][c]);
   p.newCtr("Demand", lc.gEql(DEMAND[c]));
  }
        
  for(s=0;s<NSupp;s++)            /* Keep within supply at each supplier*/
  {
   lc = new XPRBexpr();
   for(c=0; c<NCust; c++)  lc.add(x[s][c]);
   p.newCtr("Supply", lc.lEql(SUPPLY[s]) );
  }  
 
/****BOUNDS****/
  for(s=0;s<NSupp;s++)
   for(c=0; c<NCust; c++)
    if(IFVAN[s][c]!=0) x[s][c].setUB(VANCAP);

/****SOLVING + OUTPUT****/
  p.exportProb(XPRB.MPS,"delivery");  /* Write out an MPS file */

  p.setSense(XPRB.MINIM);          /* Set objective sense to minimization */
  p.lpOptimize("");                /* Solve the LP-problem */
  System.out.println("Objective: " + p.getObjVal());  /* Get objective value */
    
  for(s=0;s<NSupp;s++)             /* Print out the solution values */
   for(c=0; c<NCust; c++)
    System.out.print(x[s][c].getName() +":"+ x[s][c].getSol() +" ");
  System.out.println();    
 }

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

    /**** Initialize the stream tokenizer ****/
 static StreamTokenizer initST(FileReader file)
 {
  StreamTokenizer st=null;

  st= new StreamTokenizer(file);   /* Initialize the stream tokenizer */
  st.commentChar('!');             /* Use the character '!' for comments */
  st.eolIsSignificant(true);       /* Return end-of-line character */
  st.ordinaryChar(',');            /* Use ',' as separator */
  st.parseNumbers();               /* Read numbers as numbers (not strings)*/ 
  return st;
 }

    /**** Read multi line data file ****/
 static void readMultiLineFile(String filename, double[][] data) throws IOException
 {
  FileReader datafile=null;
  StreamTokenizer st;
  int i=0, j=0;

  datafile = new FileReader(filename);
  st = initST(datafile);
  do
  {
   do
   { 
    st.nextToken();
   } while(st.ttype==st.TT_EOL);    /* Skip empty lines */
   while(st.ttype == st.TT_NUMBER)
   {
    data[j][i++] = st.nval;
    if(st.nextToken() != ',') { j++; i=0; break;}
    st.nextToken();
   }
  } while( st.ttype == st.TT_EOL );
  datafile.close(); 
 }

    /**** Read data from files ****/
 static void readData() throws IOException
 {
  int s,c;  

  COST = new double[NSupp][NCust];
  IFVAN = new double[NSupp][NCust];
 
/* Initialize data tables to 0: in the van data file some entries that are 
 * zero are simply left out (that is, the lines are incomplete) */
  for(s=0;s<NSupp;s++)
   for(c=0; c<NCust; c++)
   {
    COST[s][c] = 0;
    IFVAN[s][c] = 0;
   }  
        /* Read the demand data file */
 readMultiLineFile(COSTFILE,COST);

        /* Read the van data file */
 readMultiLineFile(VANFILE,IFVAN);
}

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

 public static void main(String[] args)
 {
  try
  {
   readData();           /* Data input from file */
   modDelivery();        /* Problem formulation and solution */
  }
  catch(IOException e)
  {
   System.err.println(e.getMessage());
   System.exit(1);
  }
 }
} 

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