examples/notebook/contrib/organize_day.ipynb
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First, you must install ortools package in this colab.
%pip install ortools
Organizing a day in Google CP Solver.
Simple scheduling problem.
Problem formulation from ECLiPSe: Slides on (Finite Domain) Constraint Logic Programming, page 38f http://eclipse-clp.org/reports/eclipse.ppt
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
#
# No overlapping of tasks s1 and s2
#
def no_overlap(solver, s1, d1, s2, d2):
b1 = solver.IsLessOrEqualVar(s1 + d1, s2) # s1 + d1 <= s2
b2 = solver.IsLessOrEqualVar(s2 + d2, s1) # s2 + d2 <= s1
solver.Add(b1 + b2 >= 1)
def main():
# Create the solver.
solver = pywrapcp.Solver('Organizing a day')
#
# data
#
n = 4
tasks = list(range(n))
work, mail, shop, bank = tasks
durations = [4, 1, 2, 1]
# task [i,0] must be finished before task [i,1]
before_tasks = [[bank, shop], [mail, work]]
# the valid times of the day
begin = 9
end = 17
#
# declare variables
#
begins = [solver.IntVar(begin, end, 'begins[%i]% % i') for i in tasks]
ends = [solver.IntVar(begin, end, 'ends[%i]% % i') for i in tasks]
#
# constraints
#
for i in tasks:
solver.Add(ends[i] == begins[i] + durations[i])
for i in tasks:
for j in tasks:
if i < j:
no_overlap(solver, begins[i], durations[i], begins[j], durations[j])
# specific constraints
for (before, after) in before_tasks:
solver.Add(ends[before] <= begins[after])
solver.Add(begins[work] >= 11)
#
# solution and search
#
db = solver.Phase(begins + ends, solver.INT_VAR_DEFAULT,
solver.INT_VALUE_DEFAULT)
solver.NewSearch(db)
num_solutions = 0
while solver.NextSolution():
num_solutions += 1
print('begins:', [begins[i].Value() for i in tasks])
print('ends:', [ends[i].Value() for i in tasks])
print()
print('num_solutions:', num_solutions)
print('failures:', solver.Failures())
print('branches:', solver.Branches())
print('WallTime:', solver.WallTime(), 'ms')
main()