BookmarkSubscribeRSS Feed
84
Calcite | Level 5 84
Calcite | Level 5

Hi, I am trying to write a code for a transshipment procurement model from 4 plants (Ps) via 3 transshipment nodes (Ts) to 4 destination distribution centers (DCs). 

The conditon is that each node in the inflow (from Ps to Ts) and outflow (from Ts to Ds) variables need to be a multiple of 3. 

 

I have tried to do that via introducing the "lot" variable, however it doesn't work correctly when I use lot =3, but it does give a correct answer when lot size = 1.

 

Can someone kindly, help point out the mistake I am making. Thank you.

 

My Current Code -

 

proc optmodel;							
set Ps ={'P1', 'P2', 'P3', 'P4'};							
set Ds ={'D1', 'D2', 'D3', 'D4'};							
set Ts ={'T1', 'T2', 'T3'};							
number InCost{Ps, Ts} = [							
39	29	43					
40	35	43					
48	44	31					
37	39	30];					
number OutCost{Ts, Ds} = [							
34	17	36	25				
30	47	16	15				
29	22	21	23];				
number Supply{Ps} = [37	34	20	28];				
number Demand{Ds} = [18	15	21	3];				
number TransshipmentCapacity {Ts} = [37	37	43];					
number TransshipmentFixedCost{Ts} = [700	700	900];					
number ProductionFixedCost{Ps} = [420	120	240	580];				
var inflow {Ps, Ts} integer>=0;							
var outflow{Ts, Ds} integer>=0;							
number lot = 1;							
var y{Ts} binary;							
var a{Ps} binary;							
number M=1000000;							
number N=1000000;							
minimize Z = sum{i in Ps}sum{j in Ts}(inflow[i,j]*lot)*InCost[i,j]+sum{j in Ts}y[j]*TransshipmentFixedCost[j]							
+sum{i in Ps}a[i]*ProductionFixedCost[i]+sum{j in Ts}sum{k in Ds}(outflow[j,k]*lot)*OutCost[j,k];							
con SupplyConst {i in Ps}:sum{j in Ts}(inflow[i,j]*lot)  <= Supply[i];							
con DemandConst {k in Ds}:sum{j in Ts}(outflow[j,k]*lot) >= Demand[k];							
con NoStockConst{j in Ts}:sum{i in Ps}(inflow[i,j]*lot) = sum{k in Ds}(outflow[j,k]*lot);							
con TsCapConst  {j in Ts}:sum{i in Ps}(inflow[i,j]*lot) <= TransshipmentCapacity[j];							
con linkingy {j in Ts}:sum{i in Ps}(inflow[i,j]*lot)<=M*y[j];							
con linkinga {i in Ps}:sum{j in Ts}(inflow[i,j]*lot)<=N*a[i];							
solve;							
print inflow;							
print outflow;							
print y;							
print a;							
print Z;							
print {j in Ts} (sum{i in Ps}inflow[i,j]);							
print {j in Ts} (sum{k in Ds}outflow[j,k]);							
quit;
4 REPLIES 4
Ksharp
Super User

Please post it at OR forum .

84
Calcite | Level 5 84
Calcite | Level 5

Ksharp..can u please share the link of the OR forum here?

 

LinusH
Tourmaline | Level 20
@Ksharp: as Super User, you have the power to move it there 🙂
Data never sleeps

SAS Innovate 2025: Call for Content

Are you ready for the spotlight? We're accepting content ideas for SAS Innovate 2025 to be held May 6-9 in Orlando, FL. The call is open until September 25. Read more here about why you should contribute and what is in it for you!

Submit your idea!

Multiple Linear Regression in SAS

Learn how to run multiple linear regression models with and without interactions, presented by SAS user Alex Chaplin.

Find more tutorials on the SAS Users YouTube channel.

Discussion stats
  • 4 replies
  • 1527 views
  • 1 like
  • 4 in conversation