The OpenCL Interferometry Library (liboi) is a C / C++ library that aims to provide software developers with access to routines that are commonly used in interferometry. The software heavily relies on the heterogeneous computing environment targeted by the Open Compute Language (OpenCL) to target a wide range of traditional and multi-core CPUs; servers, hand-held/embedded devices, specialized hardware, and Graphical Processing Units (GPUs).

The library currently provides:

• OpenGL / OpenCL Interop (copy OpenGL image to OpenCL buffers)
• Image to Fourier transform via. a discrete Fourier Transform
• Fourier transform to interferometric data (visibility squared, bispectra)
• Image data to chi, chi squared, and log(likelihood).

To use liboi on OS X, the following are required:

• OpenCL 1.1 support (OS X 10.7 or higher)
• gcc 4.7.4 or later †
• cmake 2.8 or higher
• cfitsio and ccfits

The OS can be installed/upgraded through the Appstore. Several of the additional required libraries can be installed through MacPorts:

sudo port install gcc47
sudo port install cmake
sudo port install cfitsio

ccfits will need to be compiled and installed manually. Download and install ccfits from here NOTE: When you compile ccfits be sure to specify

export CC=/path/to/gcc
export CXX=/path/to/g++

so that gcc compiles and links the libraries. After these are installed follow the building instructions below.

If you wish to keep up with the development version, it is suggested that you also install git.

† It is possible that Xcode 4.6 (which includes Apple clang 4.2 which is based on llvm-clang 3.2svn) could compile liboi, but we haven't tested this yet.

To use liboi on a Debian / Ubuntu system, the following are should be installed:

• gcc and g++ v4.6.3 (or later)
• cmake v2.8
• cfitsio, ccfits
• An OpenGL library (optional, enables OpenCL-OpenGL interoperability)
• An OpenCL 1.1 compliant device and library

Most of these packages can be easily installed through apt-get. First the compiler, cmake, cfitsio, and ccfits:

sudo apt-get install build-essential g++ cmake libccfits0 libccfits-dev 

To enable OpenCL-OpenGL interoperability you should also install an OpenGL library. This should install the prerequisites:

sudo apt-get install libglu1-mesa libglu1-mesa-dev

For OpenCL capabilities you need to install drivers for your device. The proprietary drivers for both NVidia and ATI GPUs distributed through the package manager should supply everything that is needed.

• For NVIDIA GPUs: sudo apt-get install nvidia-current or NVidia drivers
• For AMD GPUs or AMD CPUs: sudo apt-get install fglrx or AMD graphic drivers, and then install the [OpenCL SDK] (http://developer.amd.com/tools/heterogeneous-computing/amd-accelerated-parallel-processing-app-sdk/downloads/)
• For Intel CPUs: Intel OpenCL SDK

After the OpenCL implementation is installed, ensure that the cl.hpp file got installed along with the OpenCL drivers. If it was not installed copy the liboi/include/cl.hpp into your system's OpenCL include directory.

After these are installed follow the building instructions below.

If you wish to keep up with the development version, it is suggested that you also install git via:

sudo apt-get install git

After installing the aforementioned prerequisites, you simply need to checkout a copy of LibOI

git clone https://github.com/bkloppenborg/liboi.git
cd liboi
git submodule update --init

After you have obtained a copy of the source and initialized the submodules, simply

cd build
cmake ..
make

If you have any errors in the compilation steps, please contact us.

If you have installed a library in a non-standard location, it may be necessary to override the library installation location. The following environmental variables are checked by CMake when building:

CFITSIO_ROOT_DIR    - path to directory above cfitstio.h and libcfitsio.*
CCFITS_ROOT_DIR     - path to directory above CCfits/ (the folder)
OPENCL_ROOT_DIR     - path to directory containing OpenCL
                      that is OpenCL/cl.hpp (Apple) or CL/cl.hpp (everyone else)

These can be set by typing export VARIABLE=/path/to/directory before calling cmake in the building instructions above. CMake should indicate that the directory you specified is used, rather than the default search path on your computer.

LibOI is free software, distributed under the [GNU Lesser General Public License (Version 3)](<http://www.gnu.org/licenses/lgpl.html).

If you use this software as part of a scientific publication, please cite as:

Kloppenborg, B.; Baron, F. (2012), "LibOI: The OpenCL Interferometry Library" (Version X). Available from https://github.com/bkloppenborg/liboi.