Create zebra.py

Author: Dimosts

pycona/benchmarks/zebra.py

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+import cpmpy as cp
+from cpmpy.transformations.normalize import toplevel_list
+from ..answering_queries.constraint_oracle import ConstraintOracle
+from ..problem_instance import ProblemInstance, absvar
+
+
+def construct_zebra_problem():
+    """
+    :Description: The zebra puzzle is a well-known logic puzzle. Five houses, each of a different color, are occupied by men of 
+    different nationalities, with different pets, drinks and cigarettes. The puzzle is to find out who owns the zebra.
+    The puzzle has 15 clues that help determine the solution.
+    :return: a ProblemInstance object, along with a constraint-based oracle
+    """
+    # Create a dictionary with the parameters
+    parameters = {"grid_size": 5, "num_categories": 5}
+
+    # Variables
+    # Flattened array with 25 elements, representing 5 elements for each of the 5 categories
+    grid = cp.intvar(1, 5, shape=(5, 5), name="grid")
+
+    C_T = list()
+
+    # Extract variables for readability
+    ukr, norge, eng, spain, jap = grid[0, :]  # Nationalities
+    red, blue, yellow, green, ivory = grid[1,:]  # Colors
+    oldGold, parly, kools, lucky, chest = grid[2,:]  # Cigarettes
+    zebra, dog, horse, fox, snails = grid[3,:]  # Pets
+    coffee, tea, h2o, milk, oj = grid[4,:]  # Drinks
+
+    # Add all constraints
+    C_T += [(eng == red)]  # Englishman lives in the red house
+    C_T += [(spain == dog)]  # Spaniard owns the dog
+    C_T += [(coffee == green)]  # Coffee is drunk in the green house
+    C_T += [(ukr == tea)]  # Ukrainian drinks tea
+    C_T += [(green == ivory + 1)]  # Green house is immediately right of the ivory house
+    C_T += [(oldGold == snails)]  # OldGold smoker owns snails
+    C_T += [(kools == yellow)]  # Kools are smoked in the yellow house
+    C_T += [(milk == 3)]  # Milk is drunk in the middle house
+    C_T += [(norge == 1)]  # Norwegian lives in the first house
+    C_T += [(abs(chest - fox) == 1)]  # Chesterfield smoker lives next to the man with the fox
+    C_T += [(abs(kools - horse) == 1)]  # Kools are smoked in the house next to the house with the horse
+    C_T += [(lucky == oj)]  # Lucky smoker drinks orange juice
+    C_T += [(jap == parly)]  # Japanese smokes Parliaments
+    C_T += [(abs(norge - blue) == 1)]  # Norwegian lives next to the blue house
+
+    # Each row must have different values
+    for row in grid:
+        C_T += list(cp.AllDifferent(row).decompose())
+
+    # Create the language:
+    AV = absvar(2)  # create abstract vars - as many as maximum arity
+
+    # create abstract relations using the abstract vars
+    lang = [AV[0] == AV[1], AV[0] != AV[1], AV[0] < AV[1], AV[0] > AV[1], AV[0] >= AV[1], AV[0] <= AV[1],
+            abs(AV[0] - AV[1]) == 1, abs(AV[0] - AV[1]) != 1, AV[0] - AV[1] == 1, AV[1] - AV[0] == 1] + [AV[0] == constant for constant in range(1, 6)] + [AV[0] != constant for constant in range(1, 6)]
+
+    instance = ProblemInstance(variables=grid, params=parameters, language=lang, name="zebra")
+
+    oracle = ConstraintOracle(list(set(toplevel_list(C_T))))
+
+
+
+    return instance, oracle