# NLopt Installation

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 CMake cmake build system, which means that you compile it via:

mkdir build
cd build
cmake ..
make

in the nlopt directory. Then install the NLopt libraries and header files via:

sudo make install

By default, this installs the NLopt shared library (libnlopt.so) 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 CMAKE_INSTALL_PREFIX variable of the cmake utility.

For example, suppose that you want to install into the install subdirectory of your home directory ($HOME). You would do: cmake -DCMAKE_INSTALL_PREFIX=$HOME/install ..
make
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$HOME/install/lib -lnlopt -lm -o myprogram See also below for how to change the installation directories for Octave, Matlab, and Guile plugins, if you are installing those. Note also that the -DCMAKE_INSTALL_PREFIX flag will change the location where the Python plugins are installed, so you may need to change the Python module search path via the PYTHONPATH environment variable. However, at this point you need to tell the operating system where to find the shared library, so that the runtime linker works properly. There are at least two ways to do this. First, you can use the LD_LIBRARY_PATH environment variable. For example, if you installed into the /foo/bar directory, so that the library is in /foo/bar/lib, then you would do export LD_LIBRARY_PATH=${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/ld.so.conf and then (as root) run /sbin/ldconfig. Category:NLopt

## Static libraries

By default, NLopt compiles as a shared library (also called a dynamic-link library). The alternative is to compile NLopt as a static library.

Compiling NLopt as a static library is easy. Just add -DBUILD_SHARED_LIBS=OFF to the cmake flags, as in:

cmake -DBUILD_SHARED_LIBS=OFF ..

Then you run make and make install as usual.

## 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).

### Matlab

In particular, for Matlab plugins to be installed, you should provide the Matlab installation dir, eg:

cmake -DMatlab_ROOT_DIR=/opt/matlab/RYYYYx/ ..

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

The Matlab plugins (along with help files and other .m files) are installed into INSTALL_MEX_DIR. You can override the default by passing a INSTALL_MEX_DIR to cmake, via (in addition to other cmake arguments):

cmake -DINSTALL_MEX_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).

### Octave

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 octave extension binary directory relatively to the installation prefix (usually something like /usr/local/lib/octave/2.1.73/site/oct/i486-pc-linux-gnu), and the .m script files are installed into the site extension directory relatively the the installation prefix (usually something like /usr/local/share/octave/2.1.73/site/m/). You can change these defaults by passing INSTALL_OCT_DIR and INSTALL_M_DIR, respectively, to the cmake script, via:

cmake -DINSTALL_OCT_DIR=octdir -DINSTALL_M_DIR=mdir ..

## 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_EXECUTABLE variable to set the name of the python executable:

cmake -DPYTHON_EXECUTABLE=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_EXECUTABLE and GUILE_EXECUTABLE variables to specify the locations of the guile-config and guile programs:

cmake -DGUILE_EXECUTABLE=guile GUILE_CONFIG_EXECUTABLE=guile-config ..

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

By default, the Guile plugin is installed in the guile extension directory defined relatively to the installation prefix.

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 subroutines written in C (or written in Fortran and converted to C) and C++. If you configure with:

cmake -DNLOPT_CXX=OFF ..

however, it will disable algorithms implemented in C++ (StoGO and AGS algorithms).

The resulting library has the same interface as the ordinary NLopt library, and can still be called from ordinary C, C++, and Fortran programs. However, one no longer has to link with the C++ standard libraries, which can sometimes be convenient for non-C++ programs, and allows libnlopt to be compatible with multiple C++ compilers simultaneously.