How to control the number of iterations
Answered
Hi
I'm a newbie with Python and I try to follow this MOOC : https://www.coursera.org/learn/operations-research-algorithms/home/welcome
After, installing python and Gurobi on my computer (an old computer with Windows 10), I tried to launch these lines.
from gurobipy import *
eg1= Model("eg1")
x1= eg1.addVar(lb = 0, vtype=GRB.CONTINUOUS, name="x1")
x2= eg1.addVar(lb = 0, vtype=GRB.CONTINUOUS, name="x2")
eg1.setObjective(700*x1+900*x2,GRB.MAXIMIZE)
eg1.addConstr(3*x1+5*x2 <= 3600, "resource_wood")
eg1.addConstr(x1+2*x2 <= 1600, "resource_labor")
eg1.addConstr(50*x1+20*x2 <= 4800, "resource_machine")
eg1.optimize()
This is the result (with Jupyter Lab and with VSCode :
Gurobi Optimizer version 11.0.3 build v11.0.3rc0 (win64 - Windows 10.0 (19045.2))
CPU model: Intel(R) Core(TM) i5-6400 CPU @ 2.70GHz, instruction set [SSE2|AVX|AVX2]
Thread count: 4 physical cores, 4 logical processors, using up to 4 threads
Optimize a model with 3 rows, 2 columns and 6 nonzeros
Model fingerprint: 0xeaf3d20c
Coefficient statistics:
Matrix range [1e+00, 5e+01]
Objective range [7e+02, 9e+02]
Bounds range [0e+00, 0e+00]
RHS range [2e+03, 5e+03]
Presolve removed 3 rows and 2 columns
Presolve time: 0.01s
Presolve: All rows and columns removed
Iteration Objective Primal Inf. Dual Inf. Time
0 2.1600000e+05 0.000000e+00 0.000000e+00 0s
Solved in 0 iterations and 0.01 seconds (0.00 work units)
Optimal objective 2.160000000e+05
The optimal objective should be 789473.68.
What is the problem ? From my computer ? From the code (because it's a old MOOC and something change with the new versions of Gurobi ?) ?
For your information, I launched the code from https://www.gurobi.com/documentation/current/examples/diet_py.html and the result is :
Set parameter Username
Gurobi Optimizer version 11.0.3 build v11.0.3rc0 (win64 - Windows 10.0 (19045.2))
CPU model: Intel(R) Core(TM) i5-6400 CPU @ 2.70GHz, instruction set [SSE2|AVX|AVX2]
Thread count: 4 physical cores, 4 logical processors, using up to 4 threads
Optimize a model with 4 rows, 12 columns and 39 nonzeros
Model fingerprint: 0x33ddb849
Coefficient statistics:
Matrix range [1e+00, 2e+03]
Objective range [9e-01, 3e+00]
Bounds range [7e+01, 2e+03]
RHS range [7e+01, 2e+03]
Presolve removed 0 rows and 2 columns
Presolve time: 0.10s
Presolved: 4 rows, 10 columns, 37 nonzeros
Iteration Objective Primal Inf. Dual Inf. Time
0 0.0000000e+00 1.472500e+02 0.000000e+00 0s
4 1.1828861e+01 0.000000e+00 0.000000e+00 0s
Solved in 4 iterations and 0.18 seconds (0.00 work units)
Optimal objective 1.182886111e+01
Cost: 11.8289
Buy:
hamburger 0.604514
milk 6.97014
ice cream 2.59132
Adding constraint: at most 6 servings of dairy
Gurobi Optimizer version 11.0.3 build v11.0.3rc0 (win64 - Windows 10.0 (19045.2))
CPU model: Intel(R) Core(TM) i5-6400 CPU @ 2.70GHz, instruction set [SSE2|AVX|AVX2]
Thread count: 4 physical cores, 4 logical processors, using up to 4 threads
Optimize a model with 5 rows, 12 columns and 41 nonzeros
Coefficient statistics:
Matrix range [1e+00, 2e+03]
Objective range [9e-01, 3e+00]
Bounds range [7e+01, 2e+03]
RHS range [6e+00, 2e+03]
LP warm-start: use basis
Iteration Objective Primal Inf. Dual Inf. Time
0 1.1828861e+01 5.698333e+01 0.000000e+00 0s
Solved in 0 iterations and 0.02 seconds (0.00 work units)
Infeasible model
No solution
Regards
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Gurobi Staff
This post is more than two years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support. -
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Hi Frederic,
You have a typo in your code:
eg1.addConstr(50*x1+20*x2 <= 4800, "resource_machine")
should be
eg1.addConstr(50*x1+20*x2 <= 48000, "resource_machine")
The output of diet.py looks normal.
- Riley
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