Java bindings for OpenCL
Java C++ CMake
Latest commit 75af3e7 Dec 15, 2016 @gpu Updated reference release handling
The implementation notes explain why it is difficult to
really prevent the objects from being garbage collected.


JOCL - Java Bindings for OpenCL -

Build instructions

In order to build JOCL, create a local working directory, e.g. C:\JOCLRoot, and clone the required repositories into this directory:

git clone
git clone

Building the native libraries

The native libraries of JOCL can be built with CMake and any compatible target compiler (e.g. Visual Studio or GCC):

  • Start cmake-gui,
  • Set the directory containing the sources of the JOCL project, e.g. C:\JOCLRoot\JOCL
  • Set the directory for the build files: e.g. C:\JOCLRoot\
  • Press "Configure" (and select the appropriate compiler)
  • Press "Generate"

Then, C:\JOCLRoot\ will contain the build files, e.g. the GCC makefiles or the Visual Studio project files. Compiling the project with these makefiles will place the binaries into a nativeLibraries subdirectory of the project, e.g. into C:\JOCLRoot\JOCL\nativeLibraries.

Building and packaging the external native library dependencies

JOCL itself does not have external dependencies, except for the run-time dependency to the OpenCL implementation. If you only want to compile JOCL, then you can skip this section.

This section only refers to libraries like JOCLBLAS and JOCLBlast, which require installations of external libraries (clBLAS and CLBlast, respectively). The following JOCLBlast and CLBlast, but the same process applies to all other external dependencies.

Compiling and installing CLBlast (as described in its documentation) will result in directories that contain the header files and the native libraries. In order to build JOCLBlast, the paths to these header directories and library files have to be entered in the CMake GUI, as the values of the CLBLAST_INSTALL_DIR and CLBlast_LIBRARY.

After this information has been entered, the JOCLBlast library may be compiled as described above, under Building the native libraries. The resulting native JOCLBlast library will be placed into the nativeLibraries directory of the project, for example, into C:\JOCLRoot\JOCLBlast\nativeLibraries

This library is dynamically linked against the actual CLBlast library. In order to be able to load this library, the CLBlast library must be in a specific subdirectory of the nativeLibraries folder. The name of this subdirectory is determined by the operating system and architecture that the library is compiled for. The general pattern here is


The OS here refers to the operating system, and will usually be windows, linux or apple. The ARCHITECTURE refers to the processor architecture of the target system, and will usually be x86 (for 32 bit system) or x86_64 (for 64 bit systems).

For example, on 64 bit Windows, the clblast.dll will have to be placed into the directory


There, it will be picked up by the Maven and integrated into the JAR, as described in the next section.

Building the Java libraries

The actual Java libraries can be built with Apache Maven. After the native libraries have been built as described above, change into the JOCL directory and execute

mvn clean install

This will compile the Java libraries, run the unit tests, assemble the classes (together with the native libraries), sources and JavaDocs into JAR files, and finally place all libraries into the
C:\JOCLRoot\JOCL\target directory.

Building for Android

Compiling native code for Android is a bit of a pain, so we use android-cmake to make our lives a bit easier. We first begin by installing the android-cmake toolchain file into our cmake modules path. On Linux, this is likely /usr/share/cmake-3.2/Modules/.

cd /usr/share/cmake-3.2/Modules
sudo wget

Next, we want to configure the build for our particular Android target.

mkdir build
cd build
cmake -DCMAKE_TOOLCHAIN_FILE=android.toolchain \
      -DANDROID_ABI=armeabi-v7a \
      -DCMAKE_BUILD_TYPE=Release \

This should be enough to get you started. For more advanced configuration, refer to the android-cmake documentation.

Finally, when building the final .jar file, we would like to avoid running the local tests, as the Android native libraries won't run on your local machine.

mvn clean install -DskipTests