# 13.4. Running `autogen.pl`

You can now run OMPI’s top-level `autogen.pl` script. This script will invoke the GNU Autoconf, Automake, and Libtool commands in the proper order and do a bunch of component discovery and housekeeping to setup to run OMPI’s top-level `configure` script.

Running `autogen.pl` may take a few minutes, depending on your system. It’s not very exciting to watch.

If you have a multi-processor system, enabling the multi-threaded behavior in Automake 1.11 (or newer) can result in `autogen.pl` running faster. Do this by setting the `AUTOMAKE_JOBS` environment variable to the number of processors (threads) that you want it to use before invoking `autogen.pl`. For example (you can put this in your shell startup files):

    # For bash/sh/zsh:
    export AUTOMAKE_JOBS=4

    # For csh/tcsh:
    set AUTOMAKE_JOBS 4

Important

You generally need to run `autogen.pl` whenever the top-level file `configure.ac` changes, or any files in the `config/` or `<project>/config/` directories change (these directories are where a lot of “include” files for Open MPI’s `configure` script live).

Note

You do NOT need to re-run `autogen.pl` if you modify a `Makefile.am`.