janekdererste / ffm-test

Test Repository to fiddle with the FFM-Framework

This repository is for playing with the foreign function and memory framework currently in second incubator

Set up

This project requires Java-18!!!

Open-Mpi

Download a recent Open-Mpi tar-all.

Follow the instrcutions from the open-mpi repo. For me the following commands worked:

$ tar xf openmpi-<version>.tar.bz2
$ cd openmpi-<version>
$ ./configure --prefix=<path/to/where/the/installation/should/go> --without-verbs 
...lots of output...
$ make -j 8 
...lots of output...
$ make install
...lots of output...

The --without-verbs parameter is necessary to disable Verbs according to this FAQ

Run the LinkedHelloWorld example

The LinkedHelloWorld example loads a custom C-library which exposes a hello function. The code for the program can be found in src/main/c/HelloWorld.c.

Before the native code can be called, it needs to be compiled. On a linux system with gcc installed one can execute the build.sh file. This will put HelloWorld.so binaries into the c-target folder. From there it can be called by the LinkedHelloWorld Java code.

To Run the LinkedHelloWorld class, one needs to set --add-modules jdk.incubator.foreign as a compiler option. In IntelliJ this is under:

Preferences -> Build, Execution, Development -> Compiler -> Java Compiler -> Additional command line parameters

Also, when running the program the following additional JVM-Parameters are necessary --add-modules jdk.incubator.foreign --enable-native-access ALL-UNNAMED

The output of the Program should be 10 Hello World <i> messages.

Run Hello_MPI.c and Ring.c

To get familiar with doing stuff in c, this repository contains Hello_MPI.c and Ring.c. Both have a dependency on the MPI-library. Both programs can be compiled with cmake. Cmake needs to be configured by running

$ cmake CMakeLists.txt

This will produce some files. Afterwards, both programs can be build with

$ cmake --build .

Run MPIHelloWorld

This is the Hello World example ported to Java. The following command starts the program:

$ mpirun -np 2 $HOME/jdk-18/bin/java \
 --add-modules jdk.incubator.foreign --enable-native-access ALL-UNNAMED \
 -cp ffm-test-1.0-SNAPSHOT.jar MPIHelloWorld \
 -libmpi /usr/lib/x86_64-linux-gnu/openmpi/lib/libmpi.so

The executable passed to mpirun is the java executable. The --add-modules jdk.incubator.foreign --enable-native-access ALL-UNNAMED parameters are necesarry to execute the foreign function api. -cp ffm-test-1.0-SNAPSHOT.jar MPIHelloWorld calls the executable jar and runs the MPIHelloWorld program. -libmpi /usr/lib/x86_64-linux-gnu/openmpi/lib/libmpi.so is the path of the shared mpi library. This varies depending on how open-mpi was installed. It must be passed to the program since the Java progam expects an absolute path to loaded libraries.

Run MPIRing

This works the same as the MPIHelloWorld example.