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Burglar - Use of index sets, formulating logical constraints Description Several versions of a simple knapsack problem:
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xbburg.c /******************************************************** BCL Example Problems ==================== file xbburg.c ````````````` Burglar problem, binary variable formulation. (c) 2008-2024 Fair Isaac Corporation author: S.Heipcke, Jan. 2000, rev. Mar. 2011 ********************************************************/ #include <stdio.h> #include "xprb.h" #define NItems 8 /* Number of items */ /****DATA****/ /* Item: 1 2 3 4 5 6 7 8 */ double VALUE[] = {15,100, 90, 60, 40, 15, 10, 1}; /* Value of items */ double WEIGHT[] = { 2, 20, 20, 30, 40, 30, 60, 10}; /* Weight of items */ double WTMAX = 102; /* Max weight allowed for haul */ int main(int argc, char **argv) { XPRBvar x[NItems]; XPRBctr cobj,ctr; int i; XPRBprob prob; prob=XPRBnewprob("Burglar"); /* Initialize a new problem in BCL */ /****VARIABLES****/ /* 1 if we take item i; 0 otherwise */ for(i=0;i<NItems;i++) x[i]=XPRBnewvar(prob,XPRB_BV, "x", 0, 1); /****OBJECTIVE****/ cobj = XPRBnewctr(prob,"OBJ",XPRB_N); /* Maximize the total value */ for(i=0;i<NItems;i++) XPRBaddterm(cobj,x[i],VALUE[i]); XPRBsetobj(prob,cobj); /* Select objective function */ /****CONSTRAINTS****/ ctr=XPRBnewctr(prob,"WtMax", XPRB_L); /* Weight restriction */ for(i=0;i<NItems;i++) XPRBaddterm(ctr, x[i], WEIGHT[i]); XPRBaddterm(ctr, NULL, WTMAX); /****SOLVING + OUTPUT****/ XPRBsetsense(prob,XPRB_MAXIM); /* Choose the sense of optimization */ XPRBmipoptimize(prob,""); /* Solve the MIP-problem */ printf("Objective: %g\n", XPRBgetobjval(prob)); /* Get objective value */ for(i=0;i<NItems;i++) /* Print out the solution values */ printf("%s:%g ", XPRBgetvarname(x[i]), XPRBgetsol(x[i])); printf("\n"); return 0; } | |||||||||||||||
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