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dekker.one
1# A political problem
2
3# Suppose that you are a politician trying to win an election. Your district has three
4# different types of areas - urban, suburban, and rural. These areas have, respectively,
5# 100,000, 200,000, and 50,000 registered voters. Although not all the registered voters
6# actually go to the polls, you decide that to govern effectively, you would like at least
7# half the registered voters in each of the three regions to vote for you. You are honorable
8# and would never consider supporting policies in which you do not believe. You realize,
9# however, that certain issues may be more effective in winning votes in certain places.
10# Your primary issues are building more roads, gun control, farm subsidies, and a gasoline tax
11# dedicated to improved public transit.
12# According to your campaign staff's research, you can estimate how many votes you win or lose
13# from each population segment by spending $1,000 on advertising on each issue.
14# POLICY | URBAN SUBURBAN RURAL
15# -----------------------------------------
16# build roads | -2 5 3
17# gun control | 8 2 -5
18# farm subsidies | 0 0 10
19# gasoline tax | 10 0 -2
20#
21# In this table, each entry indicates the number of thousands of either urban, suburban,
22# or rural voters who would be won over by spending $1,000 on advertising in support of
23# a particular issue. Negative entries denote votes that would be lost.
24# Your task is to figure out the minimum amount of mony that you need to spend in order to win
25# 50,000 urban votes, 10,000 suburban votes, and 25,000 rural votes.
26
27
28from minizinc import *
29
30m = Model()
31
32x1 = m.Variable(0.0,10000.0)
33x2 = m.Variable(0.0,10000.0)
34x3 = m.Variable(0.0,10000.0)
35x4 = m.Variable(0.0,10000.0)
36
37m.Constraint( -2.0*x1 + 8.0*x2 + 0.0*x3 + 10.0*x4 >= 50.0,
38 5.0*x1 + 2.0*x2 + 0.0*x3 + 0.0*x4 >= 100.0,
39 3.0*x1 - 5.0*x2 + 10.0*x3 - 2.0*x4 >= 25.0,
40 )
41
42m._debugprint()
43m.mznmodel.set_time_limit(10)
44
45m.minimize(x1+x2+x3+x4)
46
47m.next()
48
49print "Minimize cost = ", x1 + x2 + x3 + x4
50print "where x1 = ", x1
51print " x2 = ", x2
52print " x3 = ", x3
53print " x4 = ", x4