How to use arg_sort on a 'array[int] of var set of int' in Minizinc?

Here is a small model that I have. I'm trying to solve it with Chuffed. There are a lot more constraints and variables to my problem, but I tried to single out what is not working.

% Model parameters.
int: n_steps;               % Number of steps in the scheduling horizon
enum tasks;                 % Set of all task ids
enum work_centers;          % Set of all work center ids

% task_work_center[t] is the work center required to do task t
array [tasks] of work_centers: task_work_center; 

% Model variables.
% task_start[t] is the starting step of task t
array [tasks] of var 1..n_steps: task_start ::add_to_output;

% Constraints.
% Example : array[1..n] of set of int: x = [ {k | k in sum([s[j]  | j in 1..i-1])+1..sum([s[j]  | j in 1..i]) } | i in 1..n];
array[work_centers] of var set of 1..n_steps: work_center_tasks = [{task_start[t] | t in tasks where task_work_center[t]==wc} | wc in work_centers];
array[work_centers] of var int: task_permutation;

include "arg_sort.mzn";
constraint
    forall(wc in work_centers)(
        task_permutation[wc] = arg_sort(work_center_tasks[wc])  %%% Does NOT work !!!
    );

% Objective.
solve satisfy;

I get the following error :

MiniZinc: type error: no function or predicate with this signature found: `arg_sort(var set of int)' Cannot use the following functions or predicates with the same identifier: function array [int] of $$E : arg_sort(array [$$E] of $$T: x); (argument 1 expects type array[int] of int, but type var set of int given) function array [int] of var $$E : arg_sort(array [$$E] of var $$T: x); (argument 1 expects type array[int] of var int, but type var set of int given) function array [int] of $$E : arg_sort(array [$$E] of float: x); (argument 1 expects type array[int] of float, but type var set of int given) function array [int] of var $$E : arg_sort(array [$$E] of var float: x); (argument 1 expects type array[int] of var float, but type var set of int given) predicate arg_sort(array [$$E] of var $$T: x,array [int] of var $$E: p); (requires 2 arguments, but 1 given) predicate arg_sort(array [$$E] of var float: x,array [int] of var $$E: p); (requires 2 arguments, but 1 given)

Do you guys know of a way to do this ? It seems like arg_sort cannot be used on var set of int... I don't mind using another method.

Edit/Adding information : I actually know in advance the dimensions of work_center_tasks, but it varies from one work center to another. If I can model that without using sets, that would work too !

Here is a small model that I have. I'm trying to solve it with Chuffed. There are a lot more constraints and variables to my problem, but I tried to single out what is not working.

% Model parameters.
int: n_steps;               % Number of steps in the scheduling horizon
enum tasks;                 % Set of all task ids
enum work_centers;          % Set of all work center ids

% task_work_center[t] is the work center required to do task t
array [tasks] of work_centers: task_work_center; 

% Model variables.
% task_start[t] is the starting step of task t
array [tasks] of var 1..n_steps: task_start ::add_to_output;

% Constraints.
% Example : array[1..n] of set of int: x = [ {k | k in sum([s[j]  | j in 1..i-1])+1..sum([s[j]  | j in 1..i]) } | i in 1..n];
array[work_centers] of var set of 1..n_steps: work_center_tasks = [{task_start[t] | t in tasks where task_work_center[t]==wc} | wc in work_centers];
array[work_centers] of var int: task_permutation;

include "arg_sort.mzn";
constraint
    forall(wc in work_centers)(
        task_permutation[wc] = arg_sort(work_center_tasks[wc])  %%% Does NOT work !!!
    );

% Objective.
solve satisfy;

I get the following error :

MiniZinc: type error: no function or predicate with this signature found: `arg_sort(var set of int)' Cannot use the following functions or predicates with the same identifier: function array [int] of $$E : arg_sort(array [$$E] of $$T: x); (argument 1 expects type array[int] of int, but type var set of int given) function array [int] of var $$E : arg_sort(array [$$E] of var $$T: x); (argument 1 expects type array[int] of var int, but type var set of int given) function array [int] of $$E : arg_sort(array [$$E] of float: x); (argument 1 expects type array[int] of float, but type var set of int given) function array [int] of var $$E : arg_sort(array [$$E] of var float: x); (argument 1 expects type array[int] of var float, but type var set of int given) predicate arg_sort(array [$$E] of var $$T: x,array [int] of var $$E: p); (requires 2 arguments, but 1 given) predicate arg_sort(array [$$E] of var float: x,array [int] of var $$E: p); (requires 2 arguments, but 1 given)

Do you guys know of a way to do this ? It seems like arg_sort cannot be used on var set of int... I don't mind using another method.

Edit/Adding information : I actually know in advance the dimensions of work_center_tasks, but it varies from one work center to another. If I can model that without using sets, that would work too !

Share Improve this question edited yesterday asked yesterday Emilie Picard-Cantin 2903 silver badges15 bronze badges

Please comment on what you expect ⁣arg_sort(work_center_tasks[wc]) to do. It seems you are trying to call arg_sort on a var set of int, which doesn't seem to make sense because the element of the set are unordered, and it is defined that iterating over the set will always be ordered in MiniZinc. – Dekker1 Commented 9 hours ago

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Sorted by: Reset to default 0

Yes, it seems that fzn_arg_sort_set.mzn is not defined in minizinc standard library.

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How to use arg_sort on a 'array[int] of var set of int' in Minizinc? - Stack Overflow

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