Picat Constraint Programming with CP 3

Question 1

Which predicate in Picat's CP module finds a solution that minimizes a given objective expression?

Accepted Answer

solve([min(Obj)], Vars)

Answer

Passing `min(Obj)` as a solve option instructs the CP solver to use branch-and-bound to minimize the objective Obj.

Question 2

What is the purpose of `element/3` in Picat's CP module?

Accepted Answer

It accesses the Nth element of a list where N is a CP variable

Answer

`element(Index, List, Value)` constrains Value to equal List[Index] when Index is a CP variable, enabling indexed access in models.

Question 3

In a Picat CP model, what does posting `X #= Y + Z` when Y and Z are already instantiated do?

Accepted Answer

It unifies X with the sum of Y and Z via constraint propagation

Answer

When Y and Z are ground, propagation immediately determines X's value, effectively unifying X with Y+Z within the constraint store.

Question 4

Which built-in in Picat CP is used to obtain the current lower bound of a variable's domain?

Accepted Answer

fd_min(Var, Lo)

Answer

`fd_min(Var, Lo)` unifies Lo with the minimum value currently in Var's finite domain.

Question 5

What does the `cumulative/4` global constraint model in Picat CP?

Accepted Answer

Resource allocation where tasks use capacity over time

Answer

`cumulative(Starts, Durations, Resources, Limit)` ensures that at no point in time does the total resource consumption exceed Limit.

Picat Practice Test