AMPL Forum

multi2.run

File from Additional Scripts: Looping and Testing – 2

				
					# ----------------------------------------
# DANTZIG-WOLFE DECOMPOSITION FOR
# MULTI-COMMODITY TRANSPORTATION
# ----------------------------------------

model multi2.mod;
data multi2.dat;

param nIter default 0;

let {p in PROD} nPROP[p] := 0;
let {p in PROD} price_convex[p] := 1;
let {i in ORIG, j in DEST} price[i,j] := 0;

option omit_zero_rows 1;
option display_1col 0;
option display_eps .000001;

# ----------------------------------------------------------

problem MasterI: Artificial, Weight, Excess, Multi, Convex;

problem SubI {p in PROD}: Artif_Reduced_Cost[p], 
   {i in ORIG, j in DEST} Trans[i,j,p], 
   {i in ORIG} Supply[i,p], {j in DEST} Demand[j,p];

repeat { 

   let nIter := nIter + 1;
   printf "\nPHASE I -- ITERATION %d\n", nIter;

   for {p in PROD} { printf "\nPRODUCT %s\n\n", p;

      solve SubI[p];
      printf "\n";
      display {i in ORIG, j in DEST} Trans[i,j,p];

      if Artif_Reduced_Cost[p] < - 0.00001 then {
         let nPROP[p] := nPROP[p] + 1;
         let {i in ORIG, j in DEST}
            prop_ship[i,j,p,nPROP[p]] := Trans[i,j,p];
         let prop_cost[p,nPROP[p]] := 
            sum {i in ORIG, j in DEST} cost[i,j,p] * Trans[i,j,p];
      };
   };

   if min {p in PROD} Artif_Reduced_Cost[p] >= - 0.00001 then {
      printf "\n*** NO FEASIBLE SOLUTION ***\n";
      break;
   };

   solve MasterI;
   printf "\n";
   display Weight; display Multi.dual;
   display {i in ORIG, j in DEST} 
      limit[i,j] - sum {p in PROD, k in 1..nPROP[p]} 
         prop_ship[i,j,p,k] * Weight[p,k];

   if Excess <= 0.00001 then break;
   else {
      let {i in ORIG, j in DEST} price[i,j] := Multi[i,j].dual;
      let {p in PROD} price_convex[p] := Convex[p].dual;
   };
};

# ----------------------------------------------------------

printf "\nSETTING UP FOR PHASE II\n";

problem MasterII: Total_Cost, Weight, Multi, Convex;

problem SubII {p in PROD}: Reduced_Cost[p], 
   {i in ORIG, j in DEST} Trans[i,j,p], 
   {i in ORIG} Supply[i,p], {j in DEST} Demand[j,p];

solve MasterII;
printf "\n";
display Weight; display Multi.dual; display Multi.slack;

let {i in ORIG, j in DEST} price[i,j] := Multi[i,j].dual;
let {p in PROD} price_convex[p] := Convex[p].dual;

repeat {

   let nIter := nIter + 1;
   printf "\nPHASE II -- ITERATION %d\n\n", nIter;

   for {p in PROD} { printf "\nPRODUCT %s\n\n", p;

      solve SubII[p];
      printf "\n";
      display {i in ORIG, j in DEST} Trans[i,j,p];

      if Reduced_Cost[p] < - 0.00001 then  {
         let nPROP[p] := nPROP[p] + 1;
         let {i in ORIG, j in DEST}
            prop_ship[i,j,p,nPROP[p]] := Trans[i,j,p];
         let prop_cost[p,nPROP[p]] := 
            sum {i in ORIG, j in DEST} cost[i,j,p] * Trans[i,j,p];
      };
   };

   if min {p in PROD} Reduced_Cost[p] >= - 0.00001 then break;

   solve MasterII;
	
   printf "\n";
   display Weight;

   let {i in ORIG, j in DEST} price[i,j] := Multi[i,j].dual;
   let {p in PROD} price_convex[p] := Convex[p].dual;
};

# ----------------------------------------------------------

printf "\nPHASE III\n";

let {i in ORIG, j in DEST, p in PROD}
   Trans[i,j,p] := sum {k in 1..nPROP[p]} prop_ship[i,j,p,k] * Weight[p,k];

param true_Total_Cost 
   := sum {i in ORIG, j in DEST, p in PROD} cost[i,j,p] * Trans[i,j,p].val;

printf "\n";
display true_Total_Cost;
display Trans;