Having problems modelling non-linear constraints in Gurobi

Muhammad Ahsan Farooq Rajput

March 12, 2024 23:54

Jaromił Najman please help !

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Simranjit Kaur

Gurobi Staff

March 13, 2024 00:03

Hi Muhammad,

Have you tried running the computeIIS or the feasRelax method on the infeasible model? Please see the following articles:

How do I determine why my model is infeasible?
How do I use 'compute IIS' to find a subset of constraints that are causing model infeasibility?
How do I change variable and/or constraint bounds to make an infeasible model feasible using feasRelax?

Best regards,
Simran

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Muhammad Ahsan Farooq Rajput

May 03, 2024 13:56

Hi Simranjit,
I modified my code but now i am getting a key error:0 in objective function. Could you please help me ?

import gurobipy as gp
from gurobipy import GRB

# Create a new Gurobi model
model = gp.Model("production_planning")

# Define the sizes of the sets
i = 6
j = 4
m = 2

# Create sets I, J, and M
I = range(i)  # Parts set from 1 to i_n
J = range(j)  # Jobs set from 1 to j_n
M = range(m)  # Machines set from 1 to m_n

# Define the parameters for each part
h = {1: 25.10, 2: 37.25, 3: 39.24, 4: 4.27, 5: 13.56, 6: 2.18}  # Height of each part
a = {1: 569.53, 2: 464.89, 3: 779.96, 4: 122.62, 5: 390.39, 6: 178.34}  # Production area of each part
V = {1: 2867.59, 2: 2378.05, 3: 16420.91, 4: 102.83, 5: 3640.48, 6: 214.79}  # Material volume of each part

# Define the parameters for each machine
MC = 2  # Cost per unit volume of material
TC = {1: 60, 2: 80}  # Operation cost per unit time for each machine
VT = {1:0.030864, 2:0.030864} # Time for forming per unit volume of material for each machine
HT = {1: 1.4, 2: 0.7}  # Accumulated interval time per unit height for each machine
HC = 20  # Cost of human work per unit time
ST = {1: 2, 2: 1}  # Setup time needed for each machine
H = {1: 32.5, '2': 40}  # Maximum height of part that each machine can process
A = {1: 625, 2: 1600} # Maximum production area of part that each machine can process

#Decision variables
X = model.addVars(j, i, vtype=GRB.BINARY, name="X")
Y = model.addVars(m, j, vtype=GRB.BINARY, name="Y")
Z = model.addVars(j, vtype=GRB.BINARY, name="Z")      #indicator variable
JPC = model.addVars(m, j, lb=0.0, ub=1.0, vtype=GRB.CONTINUOUS, name="JPC")

model.update()

#Objective function
model.setObjective((sum(JPC[m,j] for m in M for j in J) / sum(V[i] for i in I)), GRB.MINIMIZE

Here in the objective function i have key error 0.

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Having problems modelling non-linear constraints in Gurobi

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