examples/notebook/contrib/mr_smith.ipynb
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First, you must install ortools package in this colab.
%pip install ortools
Mr Smith in Google CP Solver.
From an IF Prolog example (http://www.ifcomputer.de/) ''' The Smith family and their three children want to pay a visit but they do not all have the time to do so. Following are few hints who will go and who will not: o If Mr Smith comes, his wife will come too. o At least one of their two sons Matt and John will come. o Either Mrs Smith or Tim will come, but not both. o Either Tim and John will come, or neither will come. o If Matt comes, then John and his father will also come. '''
The answer should be: Mr_Smith_comes = 0 Mrs_Smith_comes = 0 Matt_comes = 0 John_comes = 1 Tim_comes = 1
Compare with the following models:
This model was created by Hakan Kjellerstrand ([email protected]) Also see my other Google CP Solver models: http://www.hakank.org/google_or_tools/
import sys
from ortools.constraint_solver import pywrapcp
def main():
# Create the solver.
solver = pywrapcp.Solver('Mr Smith problem')
#
# data
#
n = 5
#
# declare variables
#
x = [solver.IntVar(0, 1, 'x[%i]' % i) for i in range(n)]
Mr_Smith, Mrs_Smith, Matt, John, Tim = x
#
# constraints
#
#
# I've kept the MiniZinc constraints for clarity
# and debugging.
#
# If Mr Smith comes then his wife will come too.
# (Mr_Smith -> Mrs_Smith)
solver.Add(Mr_Smith - Mrs_Smith <= 0)
# At least one of their two sons Matt and John will come.
# (Matt \/ John)
solver.Add(Matt + John >= 1)
# Either Mrs Smith or Tim will come but not both.
# bool2int(Mrs_Smith) + bool2int(Tim) = 1 /\
# (Mrs_Smith xor Tim)
solver.Add(Mrs_Smith + Tim == 1)
# Either Tim and John will come or neither will come.
# (Tim = John)
solver.Add(Tim == John)
# If Matt comes /\ then John and his father will also come.
# (Matt -> (John /\ Mr_Smith))
solver.Add(Matt - (John * Mr_Smith) <= 0)
#
# solution and search
#
db = solver.Phase(x, solver.INT_VAR_DEFAULT, solver.INT_VALUE_DEFAULT)
solver.NewSearch(db)
num_solutions = 0
while solver.NextSolution():
num_solutions += 1
print('x:', [x[i].Value() for i in range(n)])
print()
print('num_solutions:', num_solutions)
print('failures:', solver.Failures())
print('branches:', solver.Branches())
print('WallTime:', solver.WallTime(), 'ms')
main()