ajax.gms : Ajax Paper Company Production Schedule

Description

This sample model is taken from the cybernet pds/apex sample
library of models. A paper manufacturer can produce four different
types of paper on three different machines. Given a fixed demand
schedule the objective is to find a production plan that
maximizes monthly profits.


Reference

  • CDC, PDS/APEX Sample Model Library. Control Data Corporation

Small Model of Type : LP


Category : GAMS Model library


Main file : ajax.gms

$title Ajax Paper Company Production Schedule  (AJAX,SEQ=60)

$onText
This sample model is taken from the cybernet pds/apex sample
library of models. A paper manufacturer can produce four different
types of paper on three different machines. Given a fixed demand
schedule the objective is to find a production plan that
maximizes monthly profits.


CDC, PDS/APEX Sample Model Library, 1977. Control Data Corporation

Keywords: linear programming, production planning, paper industry, micro economics,
          scheduling
$offText

Set
   m 'machines at mills' / machine-1,  machine-2,  machine-3              /
   g 'paper grades'      / 20-bond-wt, 25-bond-wt, c-bond-ext, tissue-wrp /;

Table prate(g,m) 'production rate (tons per hour)'
                  machine-1  machine-2   machine-3
   20-bond-wt            53         52          49
   25-bond-wt            51         49          44
   c-bond-ext            52         45          47
   tissue-wrp            42         44          40;

Table pcost(g,m) 'production cost     ($ per ton)'
                  machine-1  machine-2  machine-3
   20-bond-wt            76         75         73
   25-bond-wt            82         80         78
   c-bond-ext            96         95         92
   tissue-wrp            72         71         70;

Table dempr(g,*) 'demand and prices'
                  demand  price
   20-bond-wt      30000     77
   25-bond-wt      20000     81
   c-bond-ext      12000     99
   tissue-wrp       8000    105;

Parameter avail(m) 'available machine time (hours per month)'
                   / machine-1  672, machine-2  600, machine-3  480 /;

Variable
   outp(g,m) 'production        (tons per month)'
   profit    'profit               ($ per month)';

Positive Variable outp;

Equation
   cap(m)    'machine capacity (hours per month)'
   dem(g)    'demand            (tons per month)'
   pdef      'profit definition    ($ per month)';

cap(m)..  sum(g, outp(g,m)/prate(g,m)) =l= avail(m);

dem(g)..  sum(m, outp(g,m)) =e= dempr(g,"demand");

pdef..    profit =e= sum(g, dempr(g,"demand")*dempr(g,"price"))
                  -  sum((g,m), pcost(g,m)*outp(g,m));

Model ajax / all /;

solve ajax using lp maximizing profit;

$sTitle Report Definitions
Parameter
   mtr(m,*) 'machine time report'
   par(g,*) 'production allocation report';

mtr(m,"avail-h")  = avail(m);
mtr(m,"used-h")   = cap.l(m);
mtr(m,"unused-h") = avail(m) - cap.l(m);
mtr(m,"marginal") = - cap.m(m);
par(g,"demand")   = dempr(g,"demand");
par(g,"sold")     = dem.l(g);
par(g,"unsold")   = dempr(g,"demand") - dem.l(g);
par(g,"marginal") = dem.m(g);

display mtr, par, outp.l, outp.m;