Originally posted by: miroumariem

Hi, 
i have a production problem that i need to model, my problem consists of  keep producing till the stock reach its maximal level, and for the consumption of products limited to a minimal stock, when its reached, the production  starts again ... but this is not the case with my model which doesnt wate to reach the minimal stock to restart.
 

can you help me plz ?

and here is my both files of the model and the data :

 

{int}T=...;

{int}machine=...;

{int}Article=...;// product

intProdCap[machine][Article]=...;//machine capacity for produce one unit from product p

intImax[Article]=...;//maximal stock

intImin[Article]=...;//  minimal stock

intD[Article][T]=...;// Demand of article p during period T

intinvI_Prod[Article]=...;// stock initial d'article p

//  decision data

dvarint P[machine][Article][T];// quantity to produce

dvarint I[machine][Article][T];// quantity to hold

//EXPRESSIONS

dexprfloat Production =

sum(minmachine,pinArticle,tinT)P[m][p][t];

dexprfloat stockage=

sum(minmachine,pinArticle,tinT)I[m][p][t];

//ovjective function maximize the productivity

maximize(Production+stockage) ;

//    constraints

subjectto

// sign constraint

{forall(minmachine,pinArticle,tinT)                                           

    {P[m][p][t] >=0;

 

I[m][p][t]>=0; }

// capacity constraints        

forall(minmachine,pinArticle,tinT)

P[m][p][t]   <=ProdCap[m][p] ;

 

forall(minmachine,pinArticle,tinT)

 

   {

I[m][p][t] <=Imax[p];

I[m][p][t]>=Imin[p] ;

     }     

// inventory balence

forall(minmachine,pinArticle,tin1..20)

I[m][p][t+1]==I[m][p][t]+P[m][p][t+1]-D[p][t+1] ;

forall(minmachine,pinArticle)//pour t==1                            

I[m][p][1]==invI_Prod[p]+P[m][p][1]-D[p][1] ;

 

// constraint to assure when I[m][p][t]reach the maximal stock we don't produce until we reach the minimal stock but this constraint work only one day after

//reaching the maximal stock and after that the system strart to produce which is wrong !! 

forall(minmachine,pinArticle,tin1..20)     

(I[m][p][t]>=54)=> (P[m][p][t+1] ==0) ;

}

executedisplay{

writeln();

writeln(" //\\Productivité//\\  = ",Production+stockage);

}

 

and the .dat:

 

Article  = {1}; // product

invI_Prod= [24]; // initial stock

machine= {1};      // machine

Imax= [57];    // maximal stock

Imin= [5];        // minimal stock

ProdCap  = [[15]] ;     // production capacity

T= {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21}; // Period

D= [[6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6]];   // demand

 

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