Sending and receiving with MPI.COMM_WORLD.Send and MPI.COMM_WORLD.Recv

This is an example for Sending and Receiving Program in MPJExpress. Overview about  sending and receiving with MPI will be added later 🙂

package MPJExpress;
import mpi.MPI;
/**
*
* @author pbasari
*/
public class SendReceive {
      public static void main (String args[]) {
          MPI.Init(args);
          int rank = MPI.COMM_WORLD.Rank();
          int size = MPI.COMM_WORLD.Size();
        // sending
        if (rank == 0) {
        int data [] = {1, 2, 3, 4};
               for (int i = 1; i < size; i++) {
                      System.out.println(“From 0 Send to ” +i);
                      MPI.COMM_WORLD.Send(data, 0, data.length, MPI.INT, i, 0);
              }
       }
       else { // receiving
             int data [] = new int[4];
             System.out.println(“Received From 0 “);
             MPI.COMM_WORLD.Recv(data, 0, data.length, MPI.INT, 0, 0);
             for (int i = 0; i < data.length; i++)
                    System.out.println(“Rank:” + rank + “; ” + data[i]);
             }
       MPI.Finalize();
}
}

MPJExpress Tutorials

Tutorials

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Welcome to the MPIExpress tutorials! In these tutorials, you will learn a wide array of concepts about MPI (Message Passing Interface) from Wes Kendall and its implementation using Java, MPJExpress. Below are the available lessons, each of which contain example code.

The tutorials assume that the reader has a basic knowledge of Java Programming Language.

Introduction and MPI installation

• • MPI tutorial introduction
  • Getting start with MPJExpress
  • MPJExpress Installation in Netbeans IDE
  • Running an MPI Hello World application

   

  Blocking point-to-point communication

  • Sending and receiving with MPI.COMM_WORLD.Send and MPI.COMM_WORLD.Recv
  • Point-to-point communication application

  Basic collective communication

  • Collective communication introduction with MPI.COMM_WORLD.Bcast
  • Common collectives – MPI.COMM_WORLD.Scatter, MPI.COMM_WORLD.Gather, and MPI.COMM_WORLD.Allgather
  • Application example – Performing parallel rank computation with basic collectives

  Advanced collective communication

  • Using MPI.COMM_WORLD.Reduce and MPI.COMM_WORLD.Allreduce for parallel number reduction

  Groups and communicators

  • Introduction to groups and communicator

   

 

© 2017 MPJExpress Tutorial. All rights reserved.

 

MPI Tutorial Introduction

MPI Tutorial Introduction From http://mpitutorial.com/tutorials/mpi-introduction/

Brief introduction to MPI, short but clear enough!. I hope you can enjoy it. Thanks for this tutorial, Wes.

MPI Tutorial Introduction

Author: Wes Kendall

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Parallel computing is now as much a part of everyone’s life as personal computers, smart phones, and other technologies are. You obviously understand this, because you have embarked upon the MPI Tutorial website. Whether you are taking a class about parallel programming, learning for work, or simply learning it because it’s fun, you have chosen to learn a skill that will remain incredibly valuable for years to come. In my opinion, you have also taken the right path to expanding your knowledge about parallel programming – by learning the Message Passing Interface (MPI). Although MPI is lower level than most parallel programming libraries (for example, Hadoop), it is a great foundation on which to build your knowledge of parallel programming.

Before I dive into MPI, I want to explain why I made this resource. When I was in graduate school, I worked extensively with MPI. I was fortunate enough to work with important figures in the MPI community during my internships at Argonne National Laboratory and to use MPI on large supercomputing resources to do crazy things in my doctoral research. However, even with access to all of these resources and knowledgeable people, I still found that learning MPI was a difficult process.

Learning MPI was difficult for me because of three main reasons. First of all, the online resources for learning MPI were mostly outdated or not that thorough. Second, it was hard to find any resources that detailed how I could easily build or access my own cluster. And finally, the cheapest MPI book at the time of my graduate studies was a whopping 60 dollars – a hefty price for a graduate student to pay. Given how important parallel programming is in our day and time, I feel it is equally important for people to have access to better information about one of the fundamental interfaces for writing parallel applications.

Although I am by no means an MPI expert, I decided that it would be useful for me to expel all of the information I learned about MPI during graduate school in the form of easy tutorials with example code that can be executed on your very own cluster! I hope this resource will be a valuable tool for your career, studies, or life – because parallel programming is not only the present, it is the future.

A brief history of MPI

Before the 1990’s, programmers weren’t as lucky as us. Writing parallel applications for different computing architectures was a difficult and tedious task. At that time, many libraries could facilitate building parallel applications, but there was not a standard accepted way of doing it.

During this time, most parallel applications were in the science and research domains. The model most commonly adopted by the libraries was the message passing model. What is the message passing model? All it means is that an application passes messages among processes in order to perform a task. This model works out quite well in practice for parallel applications. For example, a master process might assign work to slave processes by passing them a message that describes the work. Another example is a parallel merge sorting application that sorts data locally on processes and passes results to neighboring processes to merge sorted lists. Almost any parallel application can be expressed with the message passing model.

Since most libraries at this time used the same message passing model with only minor feature differences among them, the authors of the libraries and others came together at the Supercomputing 1992 conference to define a standard interface for performing message passing – the Message Passing Interface. This standard interface would allow programmers to write parallel applications that were portable to all major parallel architectures. It would also allow them to use the features and models they were already used to using in the current popular libraries.

By 1994, a complete interface and standard was defined (MPI-1). Keep in mind that MPI is only a definition for an interface. It was then up to developers to create implementations of the interface for their respective architectures. Luckily, it only took another year for complete implementations of MPI to become available. After its first implementations were created, MPI was widely adopted and still continues to be the de-facto method of writing message-passing applications.

An accurate representation of the first MPI programmers.

MPI’s design for the message passing model

Before starting the tutorial, I will cover a couple of the classic concepts behind MPI’s design of the message passing model of parallel programming. The first concept is the notion of a communicator. A communicator defines a group of processes that have the ability to communicate with one another. In this group of processes, each is assigned a unique rank, and they explicitly communicate with one another by their ranks.

The foundation of communication is built upon send and receive operations among processes. A process may send a message to another process by providing the rank of the process and a unique tag to identify the message. The receiver can then post a receive for a message with a given tag (or it may not even care about the tag), and then handle the data accordingly. Communications such as this which involve one sender and receiver are known as point-to-point communications.

There are many cases where processes may need to communicate with everyone else. For example, when a master process needs to broadcast information to all of its worker processes. In this case, it would be cumbersome to write code that does all of the sends and receives. In fact, it would often not use the network in an optimal manner. MPI can handle a wide variety of these types of collective communications that involve all processes.

Instalasi MPJExpress di Netbeans

Kali ini, kita akan menggunakan Netbeans IDE untuk pemrograman paralel. Penulis menggunakan Netbeans versi 8.2 dengan spesifikasi sebagai berikut:

• Product Version: NetBeans IDE 8.2 (Build 201609300101)
  Updates: Updates available to version NetBeans 8.2 Patch 2
  Java: 1.8.0_112; Java HotSpot(TM) 64-Bit Server VM 25.112-b15
  Runtime: Java(TM) SE Runtime Environment 1.8.0_112-b15
  System: Windows 7 version 6.1 running on amd64; Cp1252; en_US (nb)
  User directory: C:\Users\Toshiba\AppData\Roaming\NetBeans\8.2
  Cache directory: C:\Users\Toshiba\AppData\Local\NetBeans\Cache\8.2

Langkah-langkah instalasi sebagai berikut:

Buat project baru: Pada contoh berikut ini, project diberi nama MPJExpress

Tambahkan library. Klik kanan pada paket Libraries sehingga muncul tampilan berikut:

Pilih JAR/Folder. Cari folder C:\mpj\lib; pilih file mpj.jar seperti pada gambar berikut ini:

Tekan tombol open. Pastikan library mpj.jar sudah ditambahkan ke paket libraries seperti pada gambar berikut ini:

Siapkan lingkungan virtual machine untuk MPJExpress sebagai berikut:

Customisasi configurasi seperti pada gambar berikut ini:

Sehingga muncul tampilan berikut ini. Lakukan pemilihan New Confif seperti pada gambar berikut ini:

Isilah configurasi baru tersebut, beri nama MPJExpress seperti pada gambar berikut ini:

 

Tekan tombol OK. Lalu lengkapi isian Working Directory dan VM Option sebagai berikut:

• Working Directory: C:\mpj\mpj-user
• VM Option:-jar C:\mpj\lib\starter.jar -np 4

(empat menunjukkan banyaknya pemroses yang digunakan sebagai virtual machine). Configurasi akhir menjadi sebagai berikut:

Tekan tombol OK.

Gunakan configurasi MPJExpress ini sebagai configurasi utama ketika mengcompile dan running program Paralel.

Berikut contoh program parallel HelloWorld dan hasil eksekusinya di Netbeans IDE:

Demikian instalasi MPJExpress di Netbeans IDE dan contoh program HelloWorld dengan 4 elemen pemroses.

 

Getting Started with MPJ Express

This section shows how MPJ Express programs can be executed in the multicore, cluster and hybrid configuration

Pre-requisites

• Java 1.6 (stable) or higher (Mandatory).
• Apache ant 1.6.2 or higher (Optional): ant is required for compiling MPJ Express source code.
• Perl (Optional): MPJ Express needs Perl for compiling source code because some of the Java code is generated from Perl templates. The build file will generate Java files from Perl templates if it detects perl on the machine. It is a good idea to install Perl if you want to do some development with MPJ Express.
• A native MPI library (Optional):  Native MPI library such as MS-MPI is required for running MPJ Express in cluster configuration with native device.
• Visual Studio (Optional): MPJ Express needs Visual Studio to build JNI wrapper library for the native device

Installing MPJ Express

This section outlines steps to download and install MPJ Express software.

1. Download MPJ Express and unpack it
2. Assuming unpacked     ‘mpj     express’     is      in     ‘c:\mpj’,     Right-click     My ComputeràPropertiesàAdvanced tabàEnvironment Variables and export the following system variables (user variables are not enough)
   • Set the value of variable  MPJ_HOME as c:\mpj
   • Append the value of variable Path as c:\mpj\bin

Compiling and Running User Applications

This section shows how to compile a simple Hello World parallel Java program.

1. Write Hello World MPJ Express program and save it as HelloWorld.java

import mpi.MPI;

/**
*
* @author pbasari
*/

public class HelloWorld {
     public static void main(String args[]) throws Exception {
         MPI.Init(args);
         int me = MPI.COMM_WORLD.Rank();
         int size = MPI.COMM_WORLD.Size();
         System.out.println(“Hi from <“+me+”>”);
         MPI.Finalize();
     }
}

2. Compile: javac -cp .;%MPJ_HOME%/lib/mpj.jar HelloWorld.java
3. Running  (Multi-core Configuration): mpjrun.bat -np 2 HelloWorld

Example:

C:\mpj\mpj-user>javac -cp .;%MPJ_HOME%/lib/mpj.jar HelloWorld.java
C:\mpj\mpj-user>mpjrun.bat -np 2 HelloWorld
MPJ Express (0.40) is started in the multicore configuration
Hi from <1>
Hi from <0>