Reading and optimizing a model
There are several ways to access the Gurobi Interactive Shell.
From Mac OS, you can simply type gurobi.sh from the command prompt. If you've installed a Python IDE, the shell will also be available from that environment.
Once the optimizer has started, you are ready to load and optimize a
model. We'll consider model
Using license file /Library/gurobi/gurobi.lic
Set parameter LogFile to value gurobi.log
Gurobi Interactive Shell, Version 9.0.1
Copyright (c) 2020, Gurobi Optimization, LLC
Type "help()" for help
gurobi> m = read('/Library/gurobi901/mac64/examples/data/coins.lp')
Read LP format model from file /Library/gurobi901/mac64/examples/data/coins.lp
Reading time = 0.01 seconds : 4 rows, 9 columns, 16 nonzeros
Gurobi Optimizer version 9.0.1 build v9.0.1rc0 (mac64)
Optimize a model with 4 rows, 9 columns and 16 nonzeros Model fingerprint: 0xa0c5449c Variable types: 4 continuous, 5 integer (0 binary) Coefficient statistics: Matrix range [6e-02, 7e+00] Objective range [1e-02, 1e+00] Bounds range [5e+01, 1e+03] RHS range [0e+00, 0e+00] Found heuristic solution: objective -0.0000000 Presolve removed 1 rows and 5 columns Presolve time: 0.00s Presolved: 3 rows, 4 columns, 9 nonzeros Variable types: 0 continuous, 4 integer (0 binary) Root relaxation: objective 1.134615e+02, 2 iterations, 0.00 seconds Nodes | Current Node | Objective Bounds | Work Expl Unexpl | Obj Depth IntInf | Incumbent BestBd Gap | It/Node Time 0 0 113.46154 0 1 -0.00000 113.46154 - - 0s H 0 0 113.4500000 113.46154 0.01% - 0s 0 0 113.46154 0 1 113.45000 113.46154 0.01% - 0s Explored 1 nodes (2 simplex iterations) in 0.01 seconds Thread count was 8 (of 8 available processors) Solution count 2: 113.45 -0 Optimal solution found (tolerance 1.00e-04) Best objective 1.134500000000e+02, best bound 1.134500000000e+02, gap 0.0000%
The read() command reads a model from a file and returns a
Model object. In the example, that object is placed into
m. There is no need to declare variables in the
Python language; you simply assign a value to a variable.
Note that read() accepts wildcard characters, so you could also have said:
gurobi> m = read('/Library/gurobi901/mac64/*/*/coin*')
Note also that Gurobi commands that read or write files will also
function correctly with compressed files. If
7zip are installed on your machine and
available in your default path, then you simply need to add the
appropriate suffix (
to the file name to read or write compressed versions.
The next statement in the example, m.optimize(), invokes the
optimize method on the
Model object (you can obtain a
list of all methods on
Model objects by typing
help(m)). The Gurobi optimization engine
finds an optimal solution with objective 113.45.