FICO
FICO Xpress Optimization Examples Repository
FICO Optimization Community FICO Xpress Optimization Home
Back to examples browserPrevious exampleNext example

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.

xbdelvrcpp.zip[download all files]

Source Files
By clicking on a file name, a preview is opened at the bottom of this page.
xbdelvr.cxx[download]
xbdlvriis.cxx[download]
xbdlvriis2iso.cxx[download]
xbdlvriis2rep.cxx[download]

Data Files





xbdlvriis.cxx

/********************************************************
  Xpress-BCL C++ Example Problems
  ===============================

  file xbdlvriis.cxx
  ``````````````````
  Transportation problem (infeasible data).
  Retrieving and printing IIS.

  (c) 2008-2024 Fair Isaac Corporation
      author: S.Heipcke, 2005, rev. Mar. 2011
********************************************************/

#include <iostream>
#include <cstdio>
#include <cstring>
#include "xprb_cpp.h"
#include "xprs.h"

using namespace std;
using namespace ::dashoptimization;

#define NSupp 10                  // Number of suppliers
#define NCust 7                   // Number of customers
#define MaxArcs 100               // Max. num. of non-zero cost values

#define VANFILE XPRBDATAPATH "/delivery/ifvan.dat"    // Van data file
#define COSTFILE XPRBDATAPATH "/delivery/cost.dat"    // Cost data file

/****DATA****/
// Supplier:      London  Luton  B'ham Bristl  Derby Stckpt   York
double SUPPLY[] = {140.0, 200.0,  50.0,  10.0, 400.0, 200.0,  20.0,
// Supplier:       Derby  Soton Scnthp
                   90.0,  30.0,  12.0};
// Customer:       London Livpol Doncst   York   Hull  Manchr Shffld
double DEMAND[] = {1230.3, 560.4, 117.1, 592.8, 310.0, 1247.0,  86.0};

double COST[NSupp][NCust];        // Cost per supplier-customer pair

double IFVAN[NSupp][NCust];       // Non-zero if route uses vans instead
                                  // of lorries
double VANCAP=40.0;               // Capacity on routes that use vans

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

void modDelivery(XPRBprob &p)
{
 XPRBexpr lobj, lc;
 int s,c,i;
 XPRBvar x[NSupp][NCust];

 int numv, numc, numiis, len, ncol, nrow, scode, ct;
 char *vnames, *cnames;
 int *viis,*ciis,*vsizes,*csizes;
 char **vindex,**cindex;
 double *suminfeas = NULL;

 XPRSprob op;
  
/****VARIABLES****/
 for(s=0;s<NSupp;s++)
  for(c=0; c<NCust; c++)
   x[s][c] = p.newVar(XPRBnewname("x_s%d",s));
     
/****OBJECTIVE****/
 for(s=0;s<NSupp;s++)             // Objective: Minimize total cost
  for(c=0; c<NCust; c++)
   lobj += COST[s][c]*x[s][c];
 p.setObj(p.newCtr("OBJ", lobj)); // Set objective function

/****CONSTRAINTS****/  
 for(c=0; c<4; c++)               // Satisfy demand of each customer
 {
  lc=0;
  for(s=0;s<5;s++)  lc += x[s][c];
  p.newCtr("Demand", lc >= DEMAND[c]);
 }
 for(c=4; c<NCust; c++)           // Satisfy demand of each customer
 {
  lc=0;
  for(s=5;s<NSupp;s++)  lc += x[s][c];
  p.newCtr("Demand", lc >= DEMAND[c]);
 }
        
 for(s=0;s<5;s++)                 // Keep within supply at each supplier
 {
  lc=0;
  for(c=0; c<4; c++)  lc+= x[s][c];
  p.newCtr("Supply", lc <= SUPPLY[s]);
 }          
 for(s=5;s<NSupp;s++)             // Keep within supply at each supplier
 {
  lc=0;
  for(c=4; c<NCust; c++)  lc+= x[s][c];
  p.newCtr("Supply", lc <= 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.setSense(XPRB_MINIM);          // Set objective sense to minimization
 p.lpOptimize("");                // Solve the LP-problem

 cout << "LP status: " << p.getLPStat() << endl;
 if (p.getLPStat()==XPRB_LP_OPTIMAL)
 {
  cout << "Objective: " << p.getObjVal() << endl;  // Get objective value
 }
 else if (p.getLPStat()==XPRB_LP_INFEAS)           // Get the IIS
 {
  op = p.getXPRSprob();           // Retrieve the Optimizer problem

/**** Get all IIS ****/
  numiis = p.getNumIIS();         // Generate IIS, get number of independent IIS

// Alternatively: use Optimizer functions to generate IIS
/*
  XPRSiisall(op);
  XPRSgetintattrib(op, XPRS_NUMIIS, &numiis);
*/

  cout << "Number of IIS: " << numiis << endl;

/**** IIS summary: Retrieve set sizes, including for the approximation ****/ 
  vsizes = new int[numiis+1];
  csizes = new int[numiis+1];
  suminfeas = new double[numiis+1];
  XPRSiisstatus(op, &numiis, csizes, vsizes, suminfeas, NULL);
  cout << "Size of subproblem    Sum of infeasibilities"<< endl;
  cout << "  (bounds/constr.)" << endl;
  cout << " Approx: (" << vsizes[0] << "/" << csizes[0] << ")       ";
  cout << suminfeas[0] << endl;
  for(i=1; i<=numiis;i++) {
   cout << "  IIS " << i << ": (" << vsizes[i] << "/" << csizes[i];
   cout << ")       " << suminfeas[i] << endl;
  } 
  delete [] vsizes; delete [] csizes; delete [] suminfeas;

/**** Alternatively: Enumeration with 'next' ****/
  /* Call 'iisfirst' it with argument 0 to obtain the information on the
     IIS approximation before the first 'iisnext' call */
  XPRSiisfirst(op, 0, &scode);
  ct=-1;
  while (scode==0)
  {
   ct++;
   XPRSgetiisdata(op, ct, &numc, &numv, NULL, NULL, NULL, NULL,
                  NULL, NULL, NULL, NULL);
   if (ct==0) {
     /* IIS number zero denotes the initial IIS approximation. 'getiisdata' 
        returns the [numbers of] columns and rows with nonzero reduced
        costs/duals. The subproblem defined by these nonzero reduced costs
        and duals is infeasible by itself.
	The sizes returned by 'iisstatus' for the IIS appoximation may be
	larger since it returns all columns and rows of the approximation,
	independent of their reduced cost/dual values. 
     */  
    cout << "IIS approximation: " << numv << " columns and " << numc;
    cout << " constraints with nonzero duals" << endl;
   }
   else {
     /* It's a valid IIS, so the sizes are returned */
    cout << "IIS " << ct << ":  " << numv << " bounds and " << numc;
    cout << " constraints" << endl;
   } 
   XPRSiisnext(op, &scode);
  }

/**** Obtain variable and constraint names for later use in printout ****/
                                  // Retrieve variable names
  XPRSgetintattrib(op, XPRS_ORIGINALCOLS, &ncol); 
  XPRSgetnamelist(op, 2, NULL, 0, &len, 0, ncol-1);    
                        // Get number of bytes required for retrieving names
  vnames = new char[len];
  vindex = new char*[ncol];
  XPRSgetnamelist(op, 2, vnames, len, NULL, 0, ncol-1); 
  vindex[0]=vnames;
  for(i=1; i<ncol; i++) vindex[i] =vindex[i-1]+strlen(vindex[i-1])+1;

                                  // Retrieve constraint names
  XPRSgetintattrib(op, XPRS_ORIGINALROWS, &nrow); 
  XPRSgetnamelist(op, 1, NULL, 0, &len, 0, nrow-1);    
  cnames = new char[len];
  cindex = new char*[nrow];
  XPRSgetnamelist(op, 1, cnames, len, NULL, 0, nrow-1);
  cindex[0]=cnames;
  for(i=1; i<nrow; i++) cindex[i] =cindex[i-1]+strlen(cindex[i-1])+1;

/**** Retrieve variables and constraints contained in IIS ****/
  for(s=1;s<=numiis;s++) 
  {
   XPRSgetiisdata(op, s, &numc, &numv, NULL, NULL, NULL, NULL,
                  NULL, NULL, NULL, NULL);

   ciis = new int[numc];
   viis = new int[numv];
   XPRSgetiisdata(op, s, &numc, &numv, ciis, viis, NULL, NULL,
                  NULL, NULL, NULL, NULL);
   cout << "IIS " << s << ":  " << numv << " variables, ";
   cout << numc << " constraints" << endl;
   if (numv>0)
   {
    cout << "  Variables: ";      // Print all variables in the IIS
    for(i=0;i<numv;i++) cout << vindex[viis[i]] << " ";
    cout << endl;
    delete [] viis;               // Free the array of variables
   } 
   if (numc>0)
   {
    cout << "  Constraints: ";    // Print all constraints in the IIS
    for(i=0;i<numc;i++) cout << cindex[ciis[i]] << " ";
    cout << endl;
    delete [] ciis;               // Free the array of constraints
   } 
  }
  delete [] vnames;
  delete [] cnames;
  delete [] vindex;
  delete [] cindex;
 }   
    
}

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

    /**** Read data from files ****/
void readData()
{
 FILE *datafile;
 int s,c;  

        // Initialize data tables to 0
 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
 datafile=fopen(COSTFILE,"r");
 for(s=0;s<NSupp;s++)
  XPRBreadarrlinecb(XPRB_FGETS, datafile, 99, "g,", COST[s], NCust);
 fclose(datafile);

        // Read the van data file
 datafile=fopen(VANFILE,"r");
 for(s=0;s<NSupp;s++)
  XPRBreadarrlinecb(XPRB_FGETS, datafile, 99, "g,", IFVAN[s], NCust);
 fclose(datafile);
}

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

int main(int argc, char **argv)
{
 XPRBprob p("Delivery");          // Initialize a new problem in BCL
 readData();                      // Data input from file
 modDelivery(p);                  // Problem formulation and solution

 return 0;
} 

Back to examples browserPrevious exampleNext example