Using a gurobi.env file
When you want to change the values of Gurobi parameters, you actually
have several options available for doing so. We've already discussed
parameter changes through the command-line tool (e.g.,
gurobi_cl Threads=1 coins.lp), and through interactive shell
commands (e.g., m.setParam('Threads', 1)). Each of our
language APIs also provides methods for setting parameters. The other
option we'd like to mention now is the gurobi.env file.
Whenever the Gurobi library starts, it will look for file
gurobi.env in the current working directory, and will apply any
parameter changes contained therein. This is true whether the Gurobi
library is invoked from the command-line, from the interactive shell,
or from any of the Gurobi APIs. Parameter settings are stored one per
line in this file, with the parameter name first, followed by at least
one space, followed by the desired value. Lines beginning with the
# sign are comments and are ignored. To give an example, the
following (Linux) commands:
> echo "Threads 1" > gurobi.env
> gurobi_cl coins.lp
Using license file /Library/gurobi/gurobi.lic
Using gurobi.env file
Set parameter LogFile to value gurobi.log
Set parameter Threads to value 1
Gurobi Optimizer version 9.0.1 build v9.0.1rc0 (mac64)
Copyright (c) 2019, Gurobi Optimization, LLC
Read LP format model from file coins.lp
Reading time = 0.00 seconds
: 4 rows, 9 columns, 16 nonzeros
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 0.00 seconds
Thread count was 1 (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%
would read the new value of the Threads parameter from file
gurobi.env and then optimize model coins.lp using
one thread. Note that if the same parameter is changed in both gurobi.env and in your program (or through the Gurobi
command-line), the value from gurobi.env will be overridden.
The distribution includes a sample gurobi.env file (in the
bin directory). The sample includes every parameter, with the
default value for each, but with all settings commented out.
