MiniZinc Assign Different Domain to Each Var in Array

Question

I have an array: array[backpacks] of int: capacity specifying the capacity of each backpack.

Now I want to create an array of variables which the constraint solver will have to satisfy. I want each variable to take values in domain 1..capacity where capacity corresponds to the one specified in the above array.

Would something like this work: array[backpacks] of var capacity: bagcaps ?

Or do I have to do something like: array[backpacks] of var 1..MAX: bagcaps

and then add constraints: constraint forall(i in backpacks) bagcaps[i] <= capacity[i] ?

Thank you.

score 1 · Accepted Answer · answered May 07 '17 at 07:40

There is no short cut to restrict the domain of specific element in the array declaration. The traditional version is the one you wrote last:

constraint forall(i in backpacks) bagcaps[i] <= capacity[i]);

However, you can make this as an predicate (and place it in a separate file which is then imported into the model with include). E.g. some thing like this:

set of int: backpacks = 1..6;
array[backpacks] of int: capacity = [10,4,3,7,5,3];
array[backpacks] of var 1..max(capacity): bagcaps;

solve satisfy;

predicate restrict_domains(array[int] of var int: x, array[int] of int: d) =
        forall(i in index_set(x)) ( x[i] <= d[i] );

constraint
     % forall(i in backpacks) ( bagcaps[i] <= capacity[i] ) % original
     restrict_domains(bagcaps,capacity)
;

% output [];

Note that you must still use restrict_domains as a constraint. And I recommend that you always restrict the domain in the declaration as much as possible, i.e. use the declaration using var 1..max(capacity) instead of var int.

MiniZinc Assign Different Domain to Each Var in Array

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