# User Guide for Microsoft Windows

This section contains information specific to using AMPL with Gurobi Solver. General instructions on modeling with AMPL can be found in the book AMPL: A Modeling Language for Mathematical Programming. You can find information about the AMPL book on the AMPL website: http://www.ampl.com. The AMPL website also contains sample models that you can download and solve using AMPL-Gurobi.

AMPL is a text-based program that is launched from a command window. The supplied Scrolling Window program `sw.exe` can be used to launch AMPL. To start AMPL, open the folder where AMPL is installed, run `sw.exe`, then type `ampl`. Advanced users who want to use the standard Windows command prompt instead of `sw.exe` should add the AMPL folder to the PATH environment variable. When using AMPL, you must explicitly tell AMPL to use the Gurobi solver by issuing the command:

      option solver gurobi_ampl;

If you forget to set the solver to Gurobi, you may receive an error when you try to solve a model.

Gurobi parameters are called "options" in AMPL. AMPL can control Gurobi parameters through the `option gurobi_options` command. For example,

      option gurobi_options 'presolve 2';

instructs Gurobi to use aggressive presolve. To add options to the current list of `gurobi_options`, use the command `option gurobi_options $gurobi_options`. For example,

      option gurobi_options $gurobi_options 'mipgap 0.01';

sets the MIP gap to 0.01, in addition to any existing Gurobi parameters. You can see the list of Gurobi parameters by typing

      gurobi_ampl -=

from a command prompt. A full list of Gurobi parameters for AMPL can be found in the next section.