18bac3b615
The variable vector added several deravitive variable that needlessly increased the size of the search tree. The change cuts the search tree size significantly.
117 lines
3.5 KiB
Python
117 lines
3.5 KiB
Python
# Copyright 2010 Hakan Kjellerstrand hakank@bonetmail.com
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License");
|
|
# you may not use this file except in compliance with the License.
|
|
# You may obtain a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS,
|
|
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
# See the License for the specific language governing permissions and
|
|
# limitations under the License.
|
|
|
|
"""
|
|
|
|
Least diff problem in Google CP Solver.
|
|
|
|
This model solves the following problem:
|
|
|
|
What is the smallest difference between two numbers X - Y
|
|
if you must use all the digits (0..9) exactly once.
|
|
|
|
Compare with the following models:
|
|
* Choco : http://www.hakank.org/choco/LeastDiff2.java
|
|
* ECLiPSE : http://www.hakank.org/eclipse/least_diff2.ecl
|
|
* Comet : http://www.hakank.org/comet/least_diff.co
|
|
* Tailor/Essence': http://www.hakank.org/tailor/leastDiff.eprime
|
|
* Gecode : http://www.hakank.org/gecode/least_diff.cpp
|
|
* Gecode/R: http://www.hakank.org/gecode_r/least_diff.rb
|
|
* JaCoP : http://www.hakank.org/JaCoP/LeastDiff.java
|
|
* MiniZinc: http://www.hakank.org/minizinc/least_diff.mzn
|
|
* SICStus : http://www.hakank.org/sicstus/least_diff.pl
|
|
* Zinc : http://hakank.org/minizinc/least_diff.zinc
|
|
|
|
This model was created by Hakan Kjellerstrand (hakank@bonetmail.com)
|
|
Also see my other Google CP Solver models:
|
|
http://www.hakank.org/google_cp_solver/
|
|
"""
|
|
from __future__ import print_function
|
|
from ortools.constraint_solver import pywrapcp
|
|
|
|
|
|
def main(unused_argv):
|
|
# Create the solver.
|
|
solver = pywrapcp.Solver("Least diff")
|
|
|
|
#
|
|
# declare variables
|
|
#
|
|
digits = list(range(0, 10))
|
|
a = solver.IntVar(digits, "a")
|
|
b = solver.IntVar(digits, "b")
|
|
c = solver.IntVar(digits, "c")
|
|
d = solver.IntVar(digits, "d")
|
|
e = solver.IntVar(digits, "e")
|
|
|
|
f = solver.IntVar(digits, "f")
|
|
g = solver.IntVar(digits, "g")
|
|
h = solver.IntVar(digits, "h")
|
|
i = solver.IntVar(digits, "i")
|
|
j = solver.IntVar(digits, "j")
|
|
|
|
letters = [a, b, c, d, e, f, g, h, i, j]
|
|
|
|
digit_vector = [10000,1000,100,10,1]
|
|
x = solver.ScalProd(letters[0:5],digit_vector)
|
|
y = solver.ScalProd(letters[5:],digit_vector)
|
|
diff = x - y
|
|
|
|
#
|
|
# constraints
|
|
#
|
|
solver.Add(diff > 0)
|
|
solver.Add(solver.AllDifferent(letters))
|
|
|
|
# objective
|
|
objective = solver.Minimize(diff, 1)
|
|
|
|
#
|
|
# solution
|
|
#
|
|
solution = solver.Assignment()
|
|
solution.Add(letters)
|
|
solution.Add(x)
|
|
solution.Add(y)
|
|
solution.Add(diff)
|
|
|
|
# last solution since it's a minimization problem
|
|
collector = solver.LastSolutionCollector(solution)
|
|
search_log = solver.SearchLog(100, diff)
|
|
# Note: I'm not sure what CHOOSE_PATH do, but it is fast:
|
|
# find the solution in just 4 steps
|
|
solver.Solve(solver.Phase(letters,
|
|
solver.CHOOSE_PATH,
|
|
solver.ASSIGN_MIN_VALUE),
|
|
[objective, search_log, collector])
|
|
|
|
# get the first (and only) solution
|
|
|
|
xval = collector.Value(0, x)
|
|
yval = collector.Value(0, y)
|
|
diffval = collector.Value(0, diff)
|
|
print("x:", xval)
|
|
print("y:", yval)
|
|
print("diff:", diffval)
|
|
print(xval, "-", yval, "=", diffval)
|
|
print([("abcdefghij"[i], collector.Value(0, letters[i])) for i in range(10)])
|
|
print()
|
|
print("failures:", solver.Failures())
|
|
print("branches:", solver.Branches())
|
|
print("WallTime:", solver.WallTime())
|
|
print()
|
|
|
|
if __name__ == "__main__":
|
|
main("cp sample")
|