/********************************************************
Xpress-BCL Java Example Problems
================================
file xbpurch.java
`````````````````
Purchasing problem using SOS-2.
(c) 2008 Fair Isaac Corporation
author: S.Heipcke, Jan. 2000, rev. Mar. 2011
********************************************************/
/* WARNING. This model is not for the novice, but it does contain many *
* useful ideas. *
* The formulation is tricky because the discounts are all-quantity, *
* so the graph of cost against quantity purchased is discontinuous. *
* To maintain sanity in the special ordered set formulation, we must *
* coarsen the discontinuity by stopping purchases just at the break *
* point. */
import java.io.*;
import com.dashoptimization.*;
public class xbpurch
{
static final String PARAMSFILE = System.getProperty("XPRBDATA") +
"/purchase/params.dat";
static final String MAXPERCFILE= System.getProperty("XPRBDATA") +
"/purchase/maxperc.dat";
static final String REQFILE = System.getProperty("XPRBDATA") +
"/purchase/required.dat";
static final String PRICEFILE = System.getProperty("XPRBDATA") +
"/purchase/pricebk.dat";
/****TABLES****/
static int NS; /* Number of suppliers */
static int NB; /* Number of price breaks */
static int NB2; /* Useful parameter */
static double[][] UC; /* Unit cost */
static double[][] BR; /* Breakpoints (quantities at which unit cost
changes) */
static double[][] X; /* Coarsened break points */
static double[][] C; /* Total cost at break points */
static double[] DELTA; /* Coarsening factors */
static double[] MAXPERC; /* Maximum percentage from each supplier */
static double REQ; /* Total quantity required */
static final double delta = 0.10; /* Base coarsening factor */
static XPRB bcl;
static XPRBprob p;
/***********************************************************************/
static void modPurchase()
{
XPRBexpr lobj, lc;
XPRBexpr[] lr;
int s,b;
XPRBvar[] x;
XPRBvar[][] lam;
bcl = new XPRB(); /* Initialize BCL */
p = bcl.newProb("Purchase"); /* Create a new problem in BCL */
/****VARIABLES****/
x = new XPRBvar[NS]; /* Quantity to purchase from supplier s */
for(s=0;s |
