94b2b13d
 Pedro Roque
PHACT source
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% Open Stacks problem
% Peter J. Stuckey
% 1/7/2009
include "globals.mzn";
int: c; % number of customers
int: p; % numer of products
%-- Types ---------------------------------------------------------------------
set of int: Custs = 1..c;
set of int: Prods = 1..p;
array[Custs,Prods] of 0..1: orders; % which customer orders which product
array[Custs] of int: norders = [ sum(j in Prods)(orders[i,j]) | i in Custs ];
%% total orders of each customer
%-- Decision variables --------------------------------------------------------
array[Prods] of var Prods: s; % schedule of products
%-- Auxilliary variables ------------------------------------------------------
array[Custs,0..p] of var 0..max(norders): o ; % orders filled after time t
var 0..c: objective;
%-- Constraints ---------------------------------------------------------------
constraint alldifferent(s); % each product scheduled once
constraint forall (i in Custs)(o[i,0] = 0); % no orders at time 0
constraint forall(t in 1..p, i in Custs)(o[i,t] = o[i,t-1] + orders[i,s[t]]);
constraint objective =
max(j in Prods)(
sum(i in Custs)(
bool2int( o[i,j-1] < norders[i] /\ o[i,j] > 0 )
)
);
%-- Solving objective and solution output -------------------------------------
solve ::
int_search(s, input_order, indomain_min, complete)
minimize objective;
output [
"s = \(s);\n",
"objective = \(objective);\n",
] ++ [
if t = 1 then "% " else "" endif ++
"\(o[i,t])" ++
if t = p then "\n" else " " endif
| i in Custs, t in 1..p
];
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