Using Ipopt from the command line

It is possible to solve AMPL problems with Ipopt directly from the command line. However, this requires a file in format .nl produced by ampl. If you have a model and data loaded in Ampl, you can create the corresponding .nl file with name, say, myprob.nl by using the Ampl command:

write gmyprob

There is a small .nl file available in the Ipopt distribution. It is located at Ipopt/test/mytoy.nl. We use this file in the remainder of this section. We assume that the file mytoy.nl is in the current directory and that the command ipopt is a shortcut for running the ipopt binary available in the bin directory of the installation of Ipopt.

We list below commands to perform basic tasks from the Linux prompt.

• To solve mytoy.nl from the Linux prompt, use:

  ipopt mytoy

• To see all command line options for Ipopt, use:

  ipopt -=

• To see more detailed information on all options for Ipopt:

  ipopt mytoy 'print_options_documentation yes'

• To run ipopt, setting the maximum number of iterations to 2 and print level to 4:

  ipopt mytoy 'max_iter 2 print_level 4'

If many options are to be set, they can be collected in a file ipopt.opt that is automatically read by Ipopt if present in the current directory, see Section 5.