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.

hakank · Accepted Answer · 2017-05-07 07:40:20Z

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.

CervEd · Accepted Answer · 2025-01-21 22:04:58Z

0

It's not obvious but you can do it like this:

list of set of int: doms = [
  1..1,                   % fixed value
  2..3,                   % range
  {4,6},                  % values
  -infinity..infinity,    % no-op
];
function array[$$y] of var int: assign(
  array[$$y] of set of int: domains
) = [
  let { var s: x, } in
  x | s in domains
];
array[int] of var int: x = assign(doms);
constraint trace(join("\n", [
  show(dom(x)) | x in x
]) ++ "\n");

output show(X);

Can't say for 100% but I think I have seen cases where the compiler defers the domain propagation in the method shared by hakank to run-time.

The above should guarantee to occur during flattening.

answered Jan 21 at 22:04

CervEd

4,5301 gold badge39 silver badges35 bronze badges

Collectives™ on Stack Overflow

MiniZinc Assign Different Domain to Each Var in Array

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related