PCJ is a library for Java language that helps to perform parallel and distributed calculations. The current version is able to work on the multicore systems connected with the typical interconnect such as ethernet or infiniband providing users with the uniform view across nodes.

Download PCJ library (jar file of 29.04.2017 ver. 5.0.6)  Latest (bug fixing release)!

Download PCJ manual (pdf) for PCJ 5 New!

The PCJ library can be used with no cost at BSD license. It requires Java 8 and no additional tools or comilers.  The PCJ library for Java 7 is available in the dowload section.

The source code is available at GitHub: https://github.com/hpdcj/pcj

Version 5.0.6 fixes some bugs occuring with the massive communication.

Version 5.0.3 contains support for Intel KNL chips.

Version 5 introduces asyncPut() and asyncGet() methods; put() and get() methods are now synchronous. There is new handling of shared variables. The code developed for PCJ 4 hast to be modified. For details please reffer to the JavaDoc file.

The usage should be acknowledged by reference to the PCJ web site and/or reference to the papers:

Usage of the PCJ:

Contact: bala@icm.edu.pl faramir@icm.edu.pl

PCJ was used to model C. Elegans signalling connnectome

The higly parallel application developed with PCJ was used to model C. Elegans signalling connectome. The simualtions were ferormed using more than 3000 cores of Cray XC40 at ICM University of Warsaw. The research paper has been published in PLOS Computational Bilogy: http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1005834

PhD degree of Łukasz Górski

Łukasz Górski received PhD degree in computer science based on the disertation titled: Adaptation of selected parallel algorithms to the PGAS programming model and their implementation in Java with the use of PCJ library. The PhD degree was granted by the Institute of Computer Science, Polish Academy of Sciences.

PCJ at PPAM 2017

PCJ has been presented during special tutorial session at PPAM 2017 conference in Liblin, Poland (12th International Conference on Parallel Processing and Applied Mathematics). PCJ related papers are also presented at the PGAS Applications Workshop at PPAM 2017.

PCJ 5 scales up to 196 608 cores

The PCJ application was successfuly run on more than 100 000 cores of Cray XC40 at HLRS. This achievement was possible due to the Marek Nowicki visit to HLRS sponsored by EuroLab-4-HPC (visit) and PRACE (CPU time). The PCJ benchamrks were executed together with the 2D stencil code based on the Game of Life example. The code shows excellent scalability for all cores used (4096 nodes = 196608 cores) The parallel efficiency achieved in weak scalling regime was 99.74%.

Obtaining PCJ

In order to use PCJ library you have to dowload PCJ.jar file from the PCJ web site:pcj.icm.edu.pl. The PCJ.jar should be located in the directory accessible by java compiler and java runtime, for example in the lib directory of your IDE. File you dowlnoad from website has to be renamed to PCJ.jar otherwise you have to use in the examples full name.

The PCJ.jar should be placed in your project directory (usually in the folder libs) and added to the project.

Starting PCJ application - Hello World

Starting PCJ application is simple. It can be built in the form of a single class which extends Storage class and implements StartPoint interface. The Storage class can be used to define shared variables. StartPoint interface provides necessary functionality to start required threads, enumerate them and performs initial synchronization of tasks.


PCJ.deploy() method initializes application using list of nodes provided as third argument. List of nodes contains internet address of the computers (cluster nodes) used in the simulations.


import java.io.IOException;
import org.pcj.*;

public class HelloWorld implements StartPoint {

    public static void main(String[] args) throws IOException {
        String nodesFile  = "nodes.txt";
        PCJ.deploy(HelloWorld.classnew NodesDescription("nodes.txt"));

    public void main() throws Throwable {
                System.out.println("Hello World from PCJ Thread " + PCJ.myId()
                                     + " out of " + PCJ.threadCount() );

The compilation and execution requires PCJ.jar in the path:

javac -cp .:PCJ.jar HelloWorld.java
java -cp .:PCJ.jar HelloWorld


The expected output is presented below:

wrz 23, 2016 2:00:22 AM org.pcj.internal.InternalPCJ start
INFO: PCJ version 5.0.0.SNAPSHOT-a728f5f built on 2016-09-13 00:58:48.180 CEST.
wrz 23, 2016 2:00:22 AM org.pcj.internal.InternalPCJ start
INFO: Starting HelloWorld with 4 threads (on 1 node)...
Hello World from PCJ Thread 2 out of 4
Hello World from PCJ Thread 0 out of 4
Hello World from PCJ Thread 1 out of 4
Hello World from PCJ Thread 3 out of 4
wrz 23, 2016 2:00:22 AM org.pcj.internal.InternalPCJ start
INFO: Completed HelloWorld with 4 threads (on 1 node) after 0h 0m 0s.
BUILD SUCCESSFUL (total time: 0 seconds)


The above scenario allows to run PCJ application within single Java Virtual Machine. The same code can be run using multiple JVM's.