Media Selection Problem

[Samuel]

I want to write code of Media selection problem in Python Gurobi which gives error. can anyone guide me about that code. code is given below

from gurobipy import *

# Warehouse demand in thousands of gallons

demand = [[1, 0, 1],

          [0, 1, 1],

          [1, 1, 0]]

# Plant capacity in thousands of gallons

capacity = [1, 1, 1]

# Transportation costs per thousand of gallons

Cost = [10000,20000,30000]

# Range of plants and warehouses

resource = range(len(capacity))

target_group = range(len(demand))

# Model

m = Model("media_selection")

# Transportation decision variables: how much to transport from a plant p to a warehouse w

media_selection = []

for r in resource:

    media_selection.append([])

    for t in target_group:

        media_selection[r].append(m.addVar(vtype=GRB.BINARY, name="Trans_%d,%d" % (r, t)))

# The objective is to minimize the total fixed and variable costs

m.modelSense = GRB.MINIMIZE

# Update model to integrate new variables

m.update()

# Set optimization objective - minimize sum of fixed costs

m.setObjective(quicksum(media_selection[r][t]*Cost[r][t] for r in resource for t in target_group))

# Production/Supply constraints

for r in resource:

    m.addConstr(quicksum(media_selection[r][t] for t in target_group) <= 1, "Capacity_%d" % r)

# Demand constraints

for t in target_group:

    m.addConstr(quicksum(media_selection[r][t]*target_group for r in resource for t in target_group) >= 1, "Demand_%d" % t)

# Solve

m.optimize()

# Print solution

print('\nTOTAL COSTS: %g' % m.objVal)

print('SOLUTION:')

[Sonja Mars]

Hi,

When setting the objective you are trying to access this here

Cost[r][t]

but
> Cost = [10000,20000,30000]

This Cost is a list and not a list of lists. So what you need to to would be something like Cost[r]

Additionally, this constraint:

m.addConstr(quicksum(media_selection[r][t]*target_group for r in resource for t in target_group) >= 1, "Demand_%d" % t)

seems to be wrong, as for each term of your sum you are multiplying a variable with a list. I guess, you want something like this target_group[r]. Please also see here for how to use quicksum(): http://www.gurobi.com/documentation/6.5/refman/py_quicksum.html


Best regards,
Sonja

-----------------------------------------------------------------
Dr. Sonja Mars
Gurobi Optimization

[Samuel]

Thank you for your reply  

[Samuel]

I am trying to write following formulation but i am stuck can you guide me about this 

minimize: c_m*x_m

subject to: N_tmx_m>=1 for all

                x_m belong to {0,1} for all m

Indices:

           t=target audiences

           m=advertising media

Parameters:

           N_tm incidence: audience t is covered by medium m

          c_m cost of selecting advertising medium m

Which i have code is following kindly guide me 

##Media Selection Problem by set covering 

from gurobipy import *

##Target Audience vs resource

target_audience_vs_resource=[[1,0,1],

                            [0,1,1],

                            [1,1,0]]

##Cost Function

cost_vector=[100,195,45]

# Model

m = Model("media_selection")

# Range of cost_vector and target audience_vs_resource

cost = range(len(cost_vector))

target = range(len(target_audience_vs_resource))

media_selection = []

for c in cost :

    media_selection.append([])

    for t in target:

        media_selection[c].append(m.addVar(vtype=GRB.BINARY, name="media_%d,%d" % (c, t)))

        

# The objective is to minimize the cost

m.modelSense = GRB.MINIMIZE

# Update model to integrate new variables

m.update()

# Set optimization objective minimize cost

m.setObjective(quicksum(media_selection[c][t]*cost_vector[c] for c in cost for t in target))

##

#####constraint 1

for t in target:

    m.addConstr(quicksum(media_selection[c][t]*target_audience_vs_resource[t] for c  in cost for t in target) >= 1, "Demand_%d" % t)

# Solve

m.optimize()

On Tuesday, 14 June 2016 10:00:07 UTC+5, Samuel wrote: