pykp.solvers.

minizinc

pykp.solvers.minizinc(items: list[Item], capacity: float, solver: str = 'coinbc') → Solution

Solves the knapsack problem using the MiniZinc.

Parameters:

itemslist[Item]

Array of items to consider for the knapsack.

capacityfloat

Maximum weight capacity of the knapsack.

solver: str, optional

MiniZinc solver to use. Default is “coinbc”.

Returns:

SolutionSolution

The optimal arrangement of items in the knapsack.

Examples

Solve a knapsack problem instance using MiniZinc and the COIN-OR Branch-and-Cut solver:

>>> from pykp.knapsack import Item
>>> from pykp import solvers
>>> items = np.array(
...     [
...         Item(value=10, weight=5),
...         Item(value=15, weight=10),
...         Item(value=5, weight=5),
...     ]
... )
>>> capacity = 15
>>> solvers.minizinc(items, capacity, solver="coinbc")
[(v: 25, w: 15, s: 6)]

Alternatively, construct an instance of the Knapsack class and call the solve method with “minizinc” as the method argument

>>> from pykp.knapsack import Item
>>> from pykp.knapsack import Knapsack
>>>
>>> items = [
...     Item(value=10, weight=5),
...     Item(value=15, weight=10),
...     Item(value=5, weight=5),
... ]
>>> capacity = 15
>>> instance = Knapsack(items=items, capacity=capacity)
>>> instance.solve(method="minizinc")
>>> instance.optimal_nodes
[(v: 25, w: 15, s: 6)]

Note

You should have MiniZinc 2.5.0 (or higher) installed on your system to use this solver. Refer to the MiniZinc documentation for installation instructions.

Note

The MiniZinc Gecode solver is not robust to multiple solutions, and will report only the first optimal solution found. If knowing all optimal solutions is important, consider using the branch-and-bound solver.