NLopt Installation

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Release notes
NLopt manual
License and Copyright

The installation of NLopt is fairly standard and straightforward, at least on Unix-like systems (GNU/Linux is fine). It doesn't require any particular packages to be installed except for a C compiler, although you need to have Octave and/or Matlab installed if you want to install the Octave and/or Matlab plugins, respectively.

In particular, NLopt uses the standard Autoconf configure script, which means that you compile it via:


in the nlopt directory. Then, you would switch to be the root user, or use the sudo command, to install the NLopt libraries and header files via:

make install

By default, this installs the NLopt static library (libnlopt.a) in /usr/local/lib and the NLopt header file (nlopt.h) in /usr/local/include, as well manual pages and a few other files.

In the following, we describe a few details of this installation process, including how to change the installation location.


Changing the installation directory

You may wish to install NLopt in a directory other than /usr/local, especially if you do not have administrator access to your machine. You can do this using the --prefix argument to the configure script.

For example, suppose that you want to install into the install subdirectory of your home directory ($HOME). You would do:

./configure --prefix=$HOME/install
make install

This will create the directories $HOME/install/lib etcetera and install NLopt into them. However, now when you compile code using NLopt, you will need to tell the compiler where to find the NLopt header files (using -I) and libraries (using -L) with something like:

cc -I$HOME/install/include myprogram.c -L$HOME/install/lib -lnlopt -lm -o myprogram

See also below for how to change the installation directories for Octave, Matlab, and Guile plugins, if you are installing those.

Note also that the --prefix flag will change the location where the Python plugins are installed, so you may need to change the Python module search path via the PYTHONPATH environment variable.

Shared libraries

By default, NLopt compiles as a static library. This means that each program you link to NLopt will make a separate copy of the library, which wastes a little disk space. The alternative is to compile NLopt as a shared library (also called a dynamic-link library). While more efficient in terms of disk space etcetera, shared libraries require a bit more care to install properly, which is why we don't install them by default.

Compiling NLopt as a shared library is easy. Just add --enable-shared to the configure flags, as in:

./configure --enable-shared

Then you run make and make install as usual.

However, at this point you need to tell the operating system where to find the shared library, so that the runtime linker works properly. There are at least two ways to do this. First, you can use the LD_LIBRARY_PATH environment variable. For example, if you installed into the /foo/bar directory, so that the library is in /foo/bar/lib, then you would do

export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/foo/bar/lib

in the bash shell, or

setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:/foo/bar/lib

in csh or w:tcsh.

Alternatively, in GNU/Linux systems, you can add the library directory to the system-wide file /etc/ and then (as root) run /sbin/ldconfig.

Octave and Matlab plugins

When you compile NLopt using the above commands, it will automatically compile plugins for both Matlab and GNU Octave (a free Matlab clone) if the latter programs are installed. On most current systems, Matlab and Octave plugins require NLopt to be compiled as a shared library (see above).


In particular, for Matlab plugins to be installed, you should to have the Matlab mex compiler command in your Unix PATH. Alternatively, you can specify the explicit path to the mex by passing a MEX variable to configure, via:

./configure MEX=/path/to/mex

Some versions of Matlab also require that you compile NLopt as a shared library in order to produce a Matlab plugin; see below.

By default, the Matlab plugins (along with help files and other .m files) are installed into the MATLABPATH printed out by matlab -n (which gives some directory within your Matlab installation directory), so that they will be available to all Matlab users. (This requires matlab to be in your PATH too; alternatively, you can pass MATLAB=/path/to/matlab to configure.) You can override this default (e.g. if you don't have administrator access on your machine) by passing a MEX_INSTALL_DIR to configure, via (in addition to other configure arguments):

./configure MEX_INSTALL_DIR=dir

to install the Matlab plugins in directory dir. In this case, however, when you run Matlab you will either need to run in the dir directory or explicitly add dir to your Matlab path (see the Matlab path command).


For the Octave plugins to be installed, you need to have the Octave mkoctfile program in your PATH. mkoctfile is Octave's equivalent of mex. If you are using a GNU/Linux system, and you installed Octave using one of the precompiled packages for your distribution, then you probably need to install a separate package to get mkoctfile. For example, on Debian you need to install the octave-headers package, and on Redhat you need the octave-devel package.

By default, the compiled Octave plugins (.oct files) are installed into the systemwide site/oct directory (usually something like /usr/lib/octave/2.1.73/site/oct/i486-pc-linux-gnu), and the .m script files are installed into the systemwide site/m directory (usually something like /usr/share/octave/2.1.73/site/m/). You can change these defaults by passing OCT_INSTALL_DIR and M_INSTALL_DIR, respectively, to the configure script, via:

./configure OCT_INSTALL_DIR=octdir M_INSTALL_DIR=mdir

(If you only pass OCT_INSTALL_DIR, the default M_INSTALL_DIR=$OCT_INSTALL_DIR.) In this case, however you will either need to run Octave in the directory where these files are installed or explicitly add those directories to the Octave path (see the Octave path command).

Python plugins

If Python is installed on your machine, and you configured NLopt as a shared library (see above), then NLopt will automatically compile and install a Python nlopt module. You also need NumPy to be installed, as NLopt's Python interface uses NumPy array types.

To specify a particular version or location of Python, use the PYTHON variable to set the name of the python executable:

./configure PYTHON=python

GNU Guile plugins

If Guile is installed on your machine, and you configured NLopt as a shared library (see above), then a Guile nlopt module will automatically be compiled and installed.

Note that many GNU/Linux distributions come with only the Guile program and shared libraries pre-installed; to compile the NLopt plugin you will also need the Guile programming header files, which are usually in a guile-dev or guile-devel package that you must install separately.

If you want to specify a particular version or a nonstandard location of Guile, you should use the GUILE_CONFIG and GUILE variables to specify the locations of the guile-config and guile programs:

./configure GUILE=guile GUILE_CONFIG=guile-config

(The configure script uses these programs to determine the compiler flags and installation directories for Guile plugins.)

By default, the Guile plugin is installed into the system-wide site directory (the value of the (%site-dir) function in Guile), typically something like /usr/share/guile/site. If you want to install somewhere else (e.g. if you do not have administrator access), you can specify a different directory by setting GUILE_INSTALL_DIR on the configure command line:

./configure GUILE_INSTALL_DIR=dir

Note, however, that if you do this then Guile may not know where to load the nlopt module from. You can update the Guile load path by changing the %load-path variable in Guile or using the GUILE_LOAD_PATH environment variable.

NLopt with C++ algorithms

NLopt, as-is, is callable from C, C++, and Fortran, with optional Matlab and GNU Octave plugins (and even installs an nlopt.hpp C++ header file to allow you to call it in a more C++ style). By default, it includes only subroutines written in C (or written in Fortran and converted to C), to simplify linking. If you configure with:

./configure --with-cxx

however, it will also include algorithms implemented in C++ (currently, just the StoGO algorithm), and the resulting library will be called libnlopt_cxx and is linked with -lnlopt_cxx.

The libnlopt_cxx has the same interface as the ordinary NLopt library, and can still be called from ordinary C and Fortran programs. However, to use it you must also link with the C++ standard libraries. The easiest way to do this is to link with the C++ linker: compile your source files into .o object files, and then call the C++ compiler to link these .o files with -lnlopt_cxx into your executable program.

It is because this linking process is somewhat annoying, and it only adds a single more algorithm (StoGO) to NLopt, that by default we omit StoGO to create a library that does not require the C++ standard libraries to link.

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