Constraint Programming with CP Flashcards

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

Answer: solve([min(Obj)], Vars)

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

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

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

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

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

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

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

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

Answer: fd_min(Var, Lo)

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

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

Answer: Resource allocation where tasks use capacity over time

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

In Picat, how do you express that variable X must be different from the integer constant 3?

Answer: X #\= 3

`X #\= 3` is the disequality constraint operator for finite-domain variables in Picat's CP module.

What search strategy does `[up]` specify when passed to `solve` in Picat's CP module?

Answer: Tries the largest value first during value selection

The `up` value-ordering option makes the solver try the largest value in the domain first at each choice point.