TITLE
   MRP1;

INDEX
  sku := (AJ8172, LQ8811, RN0098, NN1100, WN7342);
  sku2 := sku;
  time := (jan1,jan2,jan3,jan4,jan5,jan6,jan7,jan8);
  

DATA
  Numbertime := count(time);

  InitialInventory[sku] := (90, 300, 100, 0, 900);  
  Leadtime[sku]         := (2, 3, 4, 1, 12);
  ProdRequire[sku, sku2] := (0, 0, 0, 0, 0,  !number of sku2's required to produce a sku 
                             2, 0, 0, 0, 0,
                             1, 0, 0, 0, 0,
                             0, 1, 0, 0, 0,
                             0, 1, 0, 0, 0);
 
  ExtDemand[sku,time] := (20, 30, 10, 20, 30, 20, 30, 40,
                           0,  0,  0,  0,  0,  0,  0,  0,
                           0,  0,  0,  0,  0,  0,  0,  0,
                           0,  0,  0,  0,  0,  0,  0,  0,
                           0,  0,  0,  0,  0,  0,  0,  0);

  Lotsize[sku] := (100, 400, 100, 1, 1000); 
  TimeReverse[time] := FORMULA(Numbertime - time + 1);

DECISION VARIABLES
  Prod[sku,time];
  Order[sku,time];
 
MODEL

  MIN Obj = SUM(sku,time: TimeReverse * Order); 

SUBJECT TO
  MaterialRequirement[sku,time]:
       SUM(time=1..time-Leadtime: Order) 
     + InitialInventory 
    >=
       SUM(time=1..time: ExtDemand 
         + SUM(sku2: ProdRequire * Order[sku:=sku2])); 
           
  LotSize[sku,time]: 
       Order >= Prod * Lotsize;

  ProductionIndicator[sku,time]: 
       Prod >= Order / 10000;

BINARY
  Prod;

END