CS 159: Parallel Processing

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "CS 159: Parallel Processing"

Transcription

1 Outline: Concurrency using Java CS 159: Parallel Processing Spring 2007 Processes vs Threads Thread basics Synchronization Locks Examples Avoiding problems Immutable objects Atomic operations High"level concurrency objects Reference: index.html Processes and Threads A process is basically a self"contained execution environment Speci#cally: a process has its own memory space Threads are $lightweight% processes Threads exist within processes. Each process has at least one. Threads share the process&s resources including memory and open #les Thread Objects Each Thread is associated with an instance of the Thread class. The most straightforward way to create a thread is to instantiate a Thread object each time the application needs to initiate an asynchronous task. You can use an Executor to create or utilize pre"existing threads for you. You hand over the tasks that are required to be done.

2 First technique: De#ning and Starting a Thread define a Runnable object (the Runnable interface defines a single method, run): public class HelloRunnable implements Runnable public void run() System.out.println("Hello from a thread"); public static void main(string args[]) (new Thread(new HelloRunnable())).start(); De#ning and Starting a Thread Second technique: subclass the Thread class public class HelloThread extends Thread public void run() System.out.println("Hello from a thread"); public static void main(string args[]) (new HelloThread()).start(); The first technique is more general since your class can subclass anything, not just Thread. The sleep method of the Thread class The Thread class has a static method called sleep that will place the currently executing thread into a sleep state 'execution suspended( for a speci#c period of time. If one thread is interrupted while it is sleeping, an InterruptedException will be thrown by the sleep method of the sleeping thread. Interrupts You can interrupt a thread by invoking the interrupt method on the Thread object. For this to work properly, the interrupted thread must support its own interuption. This can be done: (a) by catching the InterruptedException---if the methods that throw the exception are often being called; (b) by checking if an interrupt has been received---if a long time can go by without calling a method that throws an InterruptedException. This is done by calling Thread.interrupted() which returns true if an interrupt has been received.

3 Sleep example public class SleepMessages public static void main(string args[]) throws InterruptedException String importantinfo[] = "Mares eat oats", "Does eat oats", "Little lambs eat ivy", "A kid will eat ivy too" ; for (int i = 0; i < importantinfo.length; i++) //Pause for 4 seconds Thread.sleep(4000); //Print a message System.out.println(importantInfo[i]); Interrupt example for (int i = 0; i < inputs.length; i++) heavycrunch(inputs[i]); //--assume a long compute time if (Thread.interrupted()) //We've been interrupted: no more crunching. return; The need for synchronization Things that can go wrong...thread interference when more than a single thread accesses shared data, there is the possibility for errors...interleaved operations may result in strange results...example of Counter object. class Counter private int c = 0; public void increment() c++; public void decrement() c--; public int value() return c; Memory consistency errors...cache memory consistency issues programmer must ensure the $happens"before% relationship example: int counter = 0; later: counter++; println(counter); if more than one thread accesses counter, then as long as we can ensure that counter++ happens before println(counter) in another thread, then the program produces the correct value.

4 More on the happens"before relationship when one thread invokes the Thread.start method, every statement that has a happens"before relationship with this statement will have a happens"before relationship with every statement executed in the new thread. Synchronization In Java, there are two synchronization mechanisms: method synchronization statement synchronization. method synchronization is achieved through the synchronized keyword. One thread at a time can enter a synchronized method. See: When one thread exits a synchronized method, all subsequent threads are guaranteed that a happensbefore relationship exists with statements executed by the #rst thread on the same object. Example public class SynchronizedCounter private int c = 0; public synchronized void increment() c++; public synchronized void decrement() c--; public synchronized int value() return c; So one way to prevent thread interference and ensure memory consistency is to handle all reads and writes of shared variables through synchronized methods. This can be inefficient. Intrinsic Locks and Synchronization Synchronization is achieved through the use of locks known as intrinsic locks or monitor locks. Every object has an intrinsic lock. If one thread wants to access an object&s #elds in an exclusive and consistent manner, it must acquire that object&s intrinsic lock before accessing the #elds and then releasing the lock after it is done. While one thread $owns% an object&s intrinsic lock, no other thread can access it.

5 Synchronized methods When a synchronized method is invoked by a thread, that thread acquires the intrinsic lock of the method&s object. The lock is released when the thread exits the method 'even through an un"caught exception(. Synchronized statements Synchronized statements are achieved by acquiring the intrinsic lock on a speci#ed object. These are synchronized Example: public void addname(string name) synchronized(this) lastname = name; namecount++; namelist.add(name); This one is not Another Example What about recursion? These objects are just for providing intrinsic locks public class TwoCounters private long c1 = 0; private long c2 = 0; private Object lock1 = new Object(); private Object lock2 = new Object(); A thread cannot acquire a lock that is owned by another thread. public void inc1() synchronized(lock1) c1++; public void inc2() synchronized(lock2) c2++; It can, however, re"acquire a lock that it already owns. This is called reentrant synchronization.

6 Atomic Access Reads and writes of reference variables and nearly all primitive type variables are atomic. Reads and writes of all variables declared volatile are atomic. Any write to a volatile variable creates a happens"before relationship with subsequent reads of that variable. Liveness The ability of a concurrent application to execute in a timely manner is known as its "liveness". Problems with liveness include "deadlock", "starvation", and "livelock". Deadlock: two threads each waiting for the other (or more complex multi-way links between threads). Starvation: shared resource is held by a greedy thread thereby not allowing other threads that need access to the resource to proceed. Livelock: a thread acts in response to another...who acts in response to the first. The actions prevent either thread from proceeding as each continues to try to respond the other indefinitely. They're not blocked...just doing useless work. Guarded Blocks Here&s a synchronization technique that provides an e)cient way to access a shared resource. The variable $joy% is set to true by some other thread. public synchronized guardedjoy() //--This guard only loops once for each special event, //--which may not be the event we're waiting for. while(joy) try wait(); catch (InterruptedException e) System.out.println( "Joy and efficiency have been achieved"); How it works The thread that has acquired the lock to the method's object finds that joy is false. The wait method releases the lock and blocks until another thread sends out notification that something has happened. The notifyall method reports to all threads waiting on the intrinsic lock owned by the notifying object which cause them to awaken. For example, this would be what the code in the notifying thread might look like: public synchronized notifyjoy() joy = true; notifyall();

7 An application to a consumer"producer problem The problem: the producer thread generates a product 'in this case a message string( that is consumed by another thread. What&s the di)culty? the consumer cannot attempt to use the product until the producer has generated it. the producer cannot place a new product in the bu*er where the consumer retrieves it until the consumer has removed it The Drop class The Drop class represents the location where the producer leaves the product and the consumer picks it up. One #eld: boolean empty; This #eld is true if there is no product waiting to be picked up by the consumer and false if there is a product Two methods: public synchronized String take() public synchronized void put(string message) See: Drop.java The String is the product that is produced and consumed. The Producer class The Consumer class The Producer class represents the entity that generates the product. One #eld: Drop drop; //--where to leave the product The class implements the Runnable interface One method: public void run() The Consumer class represents the entity that consumes the product. One #eld: Drop drop; //--where to get the product The class implements the Runnable interface One method: public void run() See: Producer.java See: Consumer.java

8 The Program Immutable Objects public class ProducerConsumerExample public static void main(string[] args) Drop drop = new Drop(); (new Thread(new Producer(drop))).start(); (new Thread(new Consumer(drop))).start(); Immutable objects are useful in concurrent applications because, since their state cannot change, they cannot become corrupted by multiple threads accessing them concurrently. Here&s an example. the class SynchronizedRGB represents a color. objects of this class have three color components 'red, green, blue( and a name 'e.g. $pitch black%( See: SynchronizedRGB.java Example Example 'continued( It is possible for an object of the SynchronizedRGB class to appear to be in an inconsistent state 'although it will always be in a consistent state(. Suppose, for example, a thread executes the following code: SynchronizedRGB color = new SynchronizedRGB(0, 0, 0, "Pitch Black");... int mycolorint = color.getrgb(); //Statement 1 String mycolorname = color.getname(); //Statement 2 Suppose another thread modi#es the color object by invoking color.set after Statement 1 but before Statement 2. Then the value of mycolorint will be inconsistent with mycolorname. One way to avoid this is to bind the two statements together in a synchronized statement: synchronized (color) int mycolorint = color.getrgb(); String mycolorname = color.getname(); If color was immutable, then this could not happen.

9 A Strategy for De#ning Immutable Objects 1. Don&t provide $setter% methods + methods that modify #elds or objects referred to by #elds. 2. Make all #elds #nal and private. 3. Don&t allow subclasses to override methods. The simplest way to do this is to declare the class as #nal. A more sophisticated approach is to make the constructor private and construct instances in factory methods. The strategy 'continued( 4. If the instance #elds include references to mutable objects, don&t allow those objects to be changed: Don&t provide methods that modify the mutable objects. Don&t share references to the mutable objects. Never store references to external, mutable objects passed to the constructor; If necessary, create copies, and store references to the copies. Similarly, create copies of your internal mutable objects when necessary to avoid returning the originals in your methods. Applying the strategy If we apply this strategy to the SynchronizedRGB class: 1. There are two setter methods in this class. The #rst one, set, arbitrarily transforms the object, and has no place in an immutable version of the class. The second one, invert, can be adapted by having it create a new object instead of modifying the existing one. 2. All #elds are already private; they are further quali#ed as #nal. 3. The class itself is declared #nal. 4. Only one #eld refers to an object, and that object is itself immutable. Therefore, no safeguards against changing the state of $contained% mutable objects are necessary. High"level Concurrency Objects Executors Java 5.0 allows us to,re"use& threads so that it&s not one thread tied to one task. Executors allow us to separate thread management from thread creation. Executor Interfaces The Executor interface has one method: voidexecute(runnable command) This method executes the given command at some time in the future. See: SynchronizedRGB.java

10 Working with Executors If r is a Runnable object, and e is an Executor object you can replace (new Thread(r)).start(); with e.execute(r); Executor implementations often rely on the presence of thread pools which are worker threads. A simple way to create an executor that uses a #xed thread pool is to invoke the newfixedthreadpool factory method in java.util.concurrent.executors For more information see the reference at Sun Microsystems: exinter.html

Java s Implementation of Concurrency, and how to use it in our applications.

Java s Implementation of Concurrency, and how to use it in our applications. Java s Implementation of Concurrency, and how to use it in our applications. 1 An application running on a single CPU often appears to perform many tasks at the same time. For example, a streaming audio/video

More information

Recapitulation of basics. Concurrent Programming in Java. Java Threads. Managing Thread objects. Concurrent Thread Execution. Starting a Thread (1)

Recapitulation of basics. Concurrent Programming in Java. Java Threads. Managing Thread objects. Concurrent Thread Execution. Starting a Thread (1) Concurrent Programming in Java bhik Roychoudhury CS 3211 National University of Singapore Recapitulation of basics Concurrency concepts Threads / Processes structuring mechanism Different from procedures

More information

CS 351 Design of Large Programs Threads and Concurrency

CS 351 Design of Large Programs Threads and Concurrency CS 351 Design of Large Programs Threads and Concurrency Brooke Chenoweth University of New Mexico Spring 2018 Concurrency in Java Java has basic concurrency support built into the language. Also has high-level

More information

Multithreaded Programming Part II. CSE 219 Stony Brook University, Department of Computer Science

Multithreaded Programming Part II. CSE 219 Stony Brook University, Department of Computer Science Multithreaded Programming Part II CSE 219 Stony Brook University, Thread Scheduling In a Java application, main is a thread on its own Once multiple threads are made Runnable the thread scheduler of the

More information

Chair of Software Engineering. Java and C# in depth. Carlo A. Furia, Marco Piccioni, Bertrand Meyer. Java: concurrency

Chair of Software Engineering. Java and C# in depth. Carlo A. Furia, Marco Piccioni, Bertrand Meyer. Java: concurrency Chair of Software Engineering Carlo A. Furia, Marco Piccioni, Bertrand Meyer Java: concurrency Outline Java threads thread implementation sleep, interrupt, and join threads that return values Thread synchronization

More information

Parallel Programming Practice

Parallel Programming Practice Parallel Programming Practice Threads and Tasks Susanne Cech Previtali Thomas Gross Last update: 2009-10-29, 09:12 Thread objects java.lang.thread Each thread is associated with an instance of the class

More information

Overview. Processes vs. Threads. Computation Abstractions. CMSC 433, Fall Michael Hicks 1

Overview. Processes vs. Threads. Computation Abstractions. CMSC 433, Fall Michael Hicks 1 CMSC 433 Programming Language Technologies and Paradigms Spring 2003 Threads and Synchronization April 1, 2003 Overview What are threads? Thread scheduling, data races, and synchronization Thread mechanisms

More information

7. MULTITHREDED PROGRAMMING

7. MULTITHREDED PROGRAMMING 7. MULTITHREDED PROGRAMMING What is thread? A thread is a single sequential flow of control within a program. Thread is a path of the execution in a program. Muti-Threading: Executing more than one thread

More information

Contents. 6-1 Copyright (c) N. Afshartous

Contents. 6-1 Copyright (c) N. Afshartous Contents 1. Classes and Objects 2. Inheritance 3. Interfaces 4. Exceptions and Error Handling 5. Intro to Concurrency 6. Concurrency in Java 7. Graphics and Animation 8. Applets 6-1 Copyright (c) 1999-2004

More information

Chair of Software Engineering. Java and C# in Depth. Prof. Dr. Bertrand Meyer. Exercise Session 8. Nadia Polikarpova

Chair of Software Engineering. Java and C# in Depth. Prof. Dr. Bertrand Meyer. Exercise Session 8. Nadia Polikarpova Chair of Software Engineering Java and C# in Depth Prof. Dr. Bertrand Meyer Exercise Session 8 Nadia Polikarpova Quiz 1: What is printed? (Java) class MyTask implements Runnable { «Everything is ok! public

More information

Threads Synchronization

Threads Synchronization Synchronization Threads Synchronization Threads share memory so communication can be based on shared references. This is a very effective way to communicate but is prone to two types of errors: Interference

More information

Need for synchronization: If threads comprise parts of our software systems, then they must communicate.

Need for synchronization: If threads comprise parts of our software systems, then they must communicate. Thread communication and synchronization There are two main aspects to Outline for Lecture 19 multithreaded programming in Java: I. Thread synchronization. thread lifecycle, and thread synchronization.

More information

The Dining Philosophers Problem CMSC 330: Organization of Programming Languages

The Dining Philosophers Problem CMSC 330: Organization of Programming Languages The Dining Philosophers Problem CMSC 0: Organization of Programming Languages Threads Classic Concurrency Problems Philosophers either eat or think They must have two forks to eat Can only use forks on

More information

CS 556 Distributed Systems

CS 556 Distributed Systems CS 556 Distributed Systems Tutorial on 4 Oct 2002 Threads A thread is a lightweight process a single sequential flow of execution within a program Threads make possible the implementation of programs that

More information

Lecture 9: Introduction to Monitors

Lecture 9: Introduction to Monitors COMP 150-CCP Concurrent Programming Lecture 9: Introduction to Monitors Dr. Richard S. Hall rickhall@cs.tufts.edu Concurrent programming February 14, 2008 Abstracting Locking Details Recall our discussion

More information

Synchronization in Java

Synchronization in Java Synchronization in Java Nelson Padua-Perez Bill Pugh Department of Computer Science University of Maryland, College Park Synchronization Overview Unsufficient atomicity Data races Locks Deadlock Wait /

More information

COMP 346 WINTER Tutorial 2 SHARED DATA MANIPULATION AND SYNCHRONIZATION

COMP 346 WINTER Tutorial 2 SHARED DATA MANIPULATION AND SYNCHRONIZATION COMP 346 WINTER 2018 1 Tutorial 2 SHARED DATA MANIPULATION AND SYNCHRONIZATION REVIEW - MULTITHREADING MODELS 2 Some operating system provide a combined user level thread and Kernel level thread facility.

More information

Threads and Parallelism in Java

Threads and Parallelism in Java Threads and Parallelism in Java Java is one of the few main stream programming languages to explicitly provide for user-programmed parallelism in the form of threads. A Java programmer may organize a program

More information

THREADS & CONCURRENCY

THREADS & CONCURRENCY 4/26/16 Announcements BRING YOUR CORNELL ID TO THE PRELIM. 2 You need it to get in THREADS & CONCURRENCY Prelim 2 is next Tonight BRING YOUR CORNELL ID! A7 is due Thursday. Our Heap.java: on Piazza (A7

More information

Performance Throughput Utilization of system resources

Performance Throughput Utilization of system resources Concurrency 1. Why concurrent programming?... 2 2. Evolution... 2 3. Definitions... 3 4. Concurrent languages... 5 5. Problems with concurrency... 6 6. Process Interactions... 7 7. Low-level Concurrency

More information

Shared Objects & Mutual Exclusion

Shared Objects & Mutual Exclusion Feb. 08, 2012 Concurrent Execution Concepts Process interference Mutual exclusion Models Model checking for interference Modeling mutual exclusion Practice Multithreaded Java programs Thread interference

More information

-Aditya Bhave CSCI-5448 Graduate Presentation

-Aditya Bhave CSCI-5448 Graduate Presentation -Aditya Bhave CSCI-5448 Graduate Presentation 04-01-2011 MSEE at CU finishing up in Summer 11 Work full time at Alticast Inc Background in Embedded Systems Media Processing Middleware Cable TV industry

More information

Animation Part 2: MoveableShape interface & Multithreading

Animation Part 2: MoveableShape interface & Multithreading Animation Part 2: MoveableShape interface & Multithreading MoveableShape Interface In the previous example, an image was drawn, then redrawn in another location Since the actions described above can apply

More information

Concurrency in Java Prof. Stephen A. Edwards

Concurrency in Java Prof. Stephen A. Edwards Concurrency in Java Prof. Stephen A. Edwards The Java Language Developed by James Gosling et al. at Sun Microsystems in the early 1990s Originally called Oak, first intended application was as an OS for

More information

Network Programming COSC 1176/1179. Lecture 6 Concurrent Programming (2)

Network Programming COSC 1176/1179. Lecture 6 Concurrent Programming (2) Network Programming COSC 1176/1179 Lecture 6 Concurrent Programming (2) Threads Recall from last week Every line of Java code is part of a thread There can be one or more threads running in parallel Each

More information

UNIT V CONCURRENT PROGRAMMING

UNIT V CONCURRENT PROGRAMMING UNIT V CONCURRENT PROGRAMMING Multi-Threading: Java provides built-in support for multithreaded programming. A multithreaded program contains two or more parts that can run concurrently. Each part of such

More information

Programming Language Concepts: Lecture 11

Programming Language Concepts: Lecture 11 Programming Language Concepts: Lecture 11 Madhavan Mukund Chennai Mathematical Institute madhavan@cmi.ac.in PLC 2011, Lecture 11, 01 March 2011 Concurrent Programming Monitors [Per Brinch Hansen, CAR Hoare]

More information

Problems with Concurrency. February 19, 2014

Problems with Concurrency. February 19, 2014 with Concurrency February 19, 2014 s with concurrency interleavings race conditions dead GUI source of s non-determinism deterministic execution model 2 / 30 General ideas Shared variable Access interleavings

More information

CS11 Java. Fall Lecture 7

CS11 Java. Fall Lecture 7 CS11 Java Fall 2006-2007 Lecture 7 Today s Topics All about Java Threads Some Lab 7 tips Java Threading Recap A program can use multiple threads to do several things at once A thread can have local (non-shared)

More information

THREADS AND CONCURRENCY

THREADS AND CONCURRENCY THREADS AND CONCURRENCY Lecture 22 CS2110 Spring 2013 Graphs summary 2 Dijkstra: given a vertex v, finds shortest path from v to x for each vertex x in the graph Key idea: maintain a 5-part invariant on

More information

Concurrency in Object Oriented Programs 4. Object-Oriented Software Development COMP4001 CSE UNSW Sydney Lecturer: John Potter

Concurrency in Object Oriented Programs 4. Object-Oriented Software Development COMP4001 CSE UNSW Sydney Lecturer: John Potter Concurrency in Object Oriented Programs 4 Object-Oriented Software Development COMP4001 CSE UNSW Sydney Lecturer: John Potter Outline Thread Control Tasks and Task Control Finding and Exploiting Parallelism

More information

JAVA CONCURRENCY FRAMEWORK. Kaushik Kanetkar

JAVA CONCURRENCY FRAMEWORK. Kaushik Kanetkar JAVA CONCURRENCY FRAMEWORK Kaushik Kanetkar Old days One CPU, executing one single program at a time No overlap of work/processes Lots of slack time CPU not completely utilized What is Concurrency Concurrency

More information

CS61B, Spring 2003 Discussion #17 Amir Kamil UC Berkeley 5/12/03

CS61B, Spring 2003 Discussion #17 Amir Kamil UC Berkeley 5/12/03 CS61B, Spring 2003 Discussion #17 Amir Kamil UC Berkeley 5/12/03 Topics: Threading, Synchronization 1 Threading Suppose we want to create an automated program that hacks into a server. Many encryption

More information

CMSC 330: Organization of Programming Languages

CMSC 330: Organization of Programming Languages CMSC 330: Organization of Programming Languages Threads Synchronization Refers to mechanisms allowing a programmer to control the execution order of some operations across different threads in a concurrent

More information

Threads and Java Memory Model

Threads and Java Memory Model Threads and Java Memory Model Oleg Šelajev @shelajev oleg@zeroturnaround.com October 6, 2014 Agenda Threads Basic synchronization Java Memory Model Concurrency Concurrency - several computations are executing

More information

Computation Abstractions. CMSC 330: Organization of Programming Languages. So, What Is a Thread? Processes vs. Threads. A computer.

Computation Abstractions. CMSC 330: Organization of Programming Languages. So, What Is a Thread? Processes vs. Threads. A computer. CMSC 330: Organization of Programming Languages Threads Computation Abstractions t1 t2 t1 t3 t2 t1 p1 p2 p3 p4 CPU 1 CPU 2 A computer t4 t5 Processes (e.g., JVM s) Threads CMSC 330 2 Processes vs. Threads

More information

CMSC 433 Programming Language Technologies and Paradigms. Composing Objects

CMSC 433 Programming Language Technologies and Paradigms. Composing Objects CMSC 433 Programming Language Technologies and Paradigms Composing Objects Composing Objects To build systems we often need to Create thread safe objects Compose them in ways that meet requirements while

More information

Multithread Computing

Multithread Computing Multithread Computing About This Lecture Purpose To learn multithread programming in Java What You Will Learn ¾ Benefits of multithreading ¾ Class Thread and interface Runnable ¾ Thread methods and thread

More information

COMPSCI 230 Threading Week8. Figure 1 Thread status diagram [http://www.programcreek.com/2009/03/thread-status/]

COMPSCI 230 Threading Week8. Figure 1 Thread status diagram [http://www.programcreek.com/2009/03/thread-status/] COMPSCI 230 Threading Week8 Figure 1 Thread status diagram [http://www.programcreek.com/2009/03/thread-status/] Synchronization Lock DeadLock Why do we need Synchronization in Java? If your code is executing

More information

Component-Based Software Engineering

Component-Based Software Engineering Component-Based Software Engineering More stuff on Threads Paul Krause Lecture 7 - Contents Basics of threads and synchronization Waiting - releasing locks Collection Plate example Choices when pausing

More information

CMSC 330: Organization of Programming Languages

CMSC 330: Organization of Programming Languages CMSC 330: Organization of Programming Languages Multithreading Multiprocessors Description Multiple processing units (multiprocessor) From single microprocessor to large compute clusters Can perform multiple

More information

The Java Memory Model

The Java Memory Model The Java Memory Model What is it and why would I want one? Jörg Domaschka. ART Group, Institute for Distributed Systems Ulm University, Germany December 14, 2009 public class WhatDoIPrint{ static int x

More information

Exercise Session Week 8

Exercise Session Week 8 Chair of Software Engineering Java and C# in Depth Carlo A. Furia, Marco Piccioni, Bertrand Meyer Exercise Session Week 8 Quiz 1: What is printed? (Java) class MyTask implements Runnable { public void

More information

JAVA and J2EE UNIT - 4 Multithreaded Programming And Event Handling

JAVA and J2EE UNIT - 4 Multithreaded Programming And Event Handling JAVA and J2EE UNIT - 4 Multithreaded Programming And Event Handling Multithreaded Programming Topics Multi Threaded Programming What are threads? How to make the classes threadable; Extending threads;

More information

Multithreaded Programming

Multithreaded Programming Multithreaded Programming Multithreaded programming basics Concurrency is the ability to run multiple parts of the program in parallel. In Concurrent programming, there are two units of execution: Processes

More information

Background. vanilladb.org

Background. vanilladb.org Background vanilladb.org Why do you need a database system? 2 To store data, why not just use a file system? 3 Advantages of a Database System It answers queries fast Q1: among a set of blog pages, find

More information

Note: Each loop has 5 iterations in the ThreeLoopTest program.

Note: Each loop has 5 iterations in the ThreeLoopTest program. Lecture 23 Multithreading Introduction Multithreading is the ability to do multiple things at once with in the same application. It provides finer granularity of concurrency. A thread sometimes called

More information

Exercise Session Week 8

Exercise Session Week 8 Chair of Software Engineering Java and C# in Depth Carlo A. Furia, Marco Piccioni, Bertrand Meyer Exercise Session Week 8 Java 8 release date Was early September 2013 Currently moved to March 2014 http://openjdk.java.net/projects/jdk8/milestones

More information

Shared-Memory and Multithread Programming

Shared-Memory and Multithread Programming Shared-Memory and Multithread Programming Pruet Boonma pruet@eng.cmu.ac.th Department of Computer Engineering Faculty of Engineering, Chiang Mai University Based on a material by: Bryan Carpenter Pervasive

More information

COMP 322: Fundamentals of Parallel Programming

COMP 322: Fundamentals of Parallel Programming COMP 322: Fundamentals of Parallel Programming https://wiki.rice.edu/confluence/display/parprog/comp322 Lecture 28: Java Threads (contd), synchronized statement Vivek Sarkar Department of Computer Science

More information

CISC 4700 L01 Network & Client-Server Programming Spring Cowell Chapter 15: Writing Threaded Applications

CISC 4700 L01 Network & Client-Server Programming Spring Cowell Chapter 15: Writing Threaded Applications CISC 4700 L01 Network & Client-Server Programming Spring 2016 Cowell Chapter 15: Writing Threaded Applications Idea: application does simultaneous activities. Example: web browsers download text and graphics

More information

Models of concurrency & synchronization algorithms

Models of concurrency & synchronization algorithms Models of concurrency & synchronization algorithms Lecture 3 of TDA383/DIT390 (Concurrent Programming) Carlo A. Furia Chalmers University of Technology University of Gothenburg SP3 2016/2017 Today s menu

More information

Concurrency - Topics. Introduction Introduction to Subprogram-Level Concurrency Semaphores Monitors Message Passing Java Threads

Concurrency - Topics. Introduction Introduction to Subprogram-Level Concurrency Semaphores Monitors Message Passing Java Threads Concurrency - Topics Introduction Introduction to Subprogram-Level Concurrency Semaphores Monitors Message Passing Java Threads 1 Introduction Concurrency can occur at four levels: Machine instruction

More information

Java Monitors. Parallel and Distributed Computing. Department of Computer Science and Engineering (DEI) Instituto Superior Técnico.

Java Monitors. Parallel and Distributed Computing. Department of Computer Science and Engineering (DEI) Instituto Superior Técnico. Java Monitors Parallel and Distributed Computing Department of Computer Science and Engineering (DEI) Instituto Superior Técnico October 19, 2010 Monteiro, Costa (DEI / IST) Parallel and Distributed Computing

More information

27/04/2012. We re going to build Multithreading Application. Objectives. MultiThreading. Multithreading Applications. What are Threads?

27/04/2012. We re going to build Multithreading Application. Objectives. MultiThreading. Multithreading Applications. What are Threads? Objectives MultiThreading What are Threads? Interrupting threads Thread properties By Võ Văn Hải Faculty of Information Technologies Summer 2012 Threads priorities Synchronization Callables and Futures

More information

Threads and Locks. CSCI 5828: Foundations of Software Engineering Lecture 09 09/22/2015

Threads and Locks. CSCI 5828: Foundations of Software Engineering Lecture 09 09/22/2015 Threads and Locks CSCI 5828: Foundations of Software Engineering Lecture 09 09/22/2015 1 Goals Cover the material presented in Chapter 2, Day 1 of our concurrency textbook Creating threads Locks Memory

More information

Threads(in Java) CSC J Paul Gibson, D311.

Threads(in Java) CSC J Paul Gibson, D311. CSC 7203 J Paul Gibson, D311 paul.gibson@telecom-sudparis.eu http://www-public.it-sudparis.eu/~gibson/teaching/csc7203/ Threads(in Java) /~gibson/teaching/csc7203/csc7203-advancedoo-l6-threads.pdf 1 Processes

More information

Concurrent Programming

Concurrent Programming Concurrency Concurrent Programming A sequential program has a single thread of control. Its execution is called a process. A concurrent program has multiple threads of control. They may be executed as

More information

Synchronization synchronization.

Synchronization synchronization. Unit 4 Synchronization of threads using Synchronized keyword and lock method- Thread pool and Executors framework, Futures and callable, Fork-Join in Java. Deadlock conditions 1 Synchronization When two

More information

What is a Thread? Why Multicore? What is a Thread? But a fast computer runs hot THREADS AND CONCURRENCY. Concurrency (aka Multitasking)

What is a Thread? Why Multicore? What is a Thread? But a fast computer runs hot THREADS AND CONCURRENCY. Concurrency (aka Multitasking) What is a Thread? 2 THREADS AND CONCURRENCY A separate process that can perform a computational task independently and concurrently with other threads Most programs have only one thread GUIs have a separate

More information

CMSC 433 Programming Language Technologies and Paradigms. Spring 2013

CMSC 433 Programming Language Technologies and Paradigms. Spring 2013 1 CMSC 433 Programming Language Technologies and Paradigms Spring 2013 Wait / Notify / NotifyAll Optimistic Retries Composition Follow-up (the risk I mentioned) ReentrantLock, Wait, Notify, NotifyAll Some

More information

Managing the Java Thread Lifecycle (Part 4)

Managing the Java Thread Lifecycle (Part 4) Managing the Java Thread Lifecycle (Part 4) Douglas C. Schmidt d.schmidt@vanderbilt.edu www.dre.vanderbilt.edu/~schmidt Institute for Software Integrated Systems Vanderbilt University Nashville, Tennessee,

More information

Synchronization II: EventBarrier, Monitor, and a Semaphore. COMPSCI210 Recitation 4th Mar 2013 Vamsi Thummala

Synchronization II: EventBarrier, Monitor, and a Semaphore. COMPSCI210 Recitation 4th Mar 2013 Vamsi Thummala Synchronization II: EventBarrier, Monitor, and a Semaphore COMPSCI210 Recitation 4th Mar 2013 Vamsi Thummala Check point: Mission in progress Master synchronization techniques Develop best practices for

More information

COMP346 Winter Tutorial 4 Synchronization Semaphores

COMP346 Winter Tutorial 4 Synchronization Semaphores COMP346 Winter 2015 Tutorial 4 Synchronization Semaphores 1 Topics Synchronization in Details Semaphores Introducing Semaphore.java 2 Synchronization What is it? An act of communication between unrelated

More information

Operating Systems. Designed and Presented by Dr. Ayman Elshenawy Elsefy

Operating Systems. Designed and Presented by Dr. Ayman Elshenawy Elsefy Operating Systems Designed and Presented by Dr. Ayman Elshenawy Elsefy Dept. of Systems & Computer Eng.. AL-AZHAR University Website : eaymanelshenawy.wordpress.com Email : eaymanelshenawy@yahoo.com Reference

More information

Synchronization. Announcements. Concurrent Programs. Race Conditions. Race Conditions 11/9/17. Purpose of this lecture. A8 released today, Due: 11/21

Synchronization. Announcements. Concurrent Programs. Race Conditions. Race Conditions 11/9/17. Purpose of this lecture. A8 released today, Due: 11/21 Announcements Synchronization A8 released today, Due: 11/21 Late deadline is after Thanksgiving You can use your A6/A7 solutions or ours A7 correctness scores have been posted Next week's recitation will

More information

Race Conditions & Synchronization

Race Conditions & Synchronization Race Conditions & Synchronization Lecture 25 Spring 2017 Gries office hours 2 A number of students have asked for time to talk over how to study for the prelim. Gries will hold office hours at the times

More information

Programming in Parallel COMP755

Programming in Parallel COMP755 Programming in Parallel COMP755 All games have morals; and the game of Snakes and Ladders captures, as no other activity can hope to do, the eternal truth that for every ladder you hope to climb, a snake

More information

Monitors CSCI 201 Principles of Software Development

Monitors CSCI 201 Principles of Software Development Monitors CSCI 201 Principles of Software Development Jeffrey Miller, Ph.D. jeffrey.miller@usc.edu Outline Monitors Program USC CSCI 201L Monitor Overview A monitor is an object with mutual exclusion and

More information

Info 408 Distributed Applications programming 2 nd semester of 2017/2018 Credits: 5 Lecturer: Dr. Antoun Yaacoub

Info 408 Distributed Applications programming 2 nd semester of 2017/2018 Credits: 5 Lecturer: Dr. Antoun Yaacoub Lebanese University Faculty of Sciences I Master 1 degree Computer Sciences Info 408 Distributed Applications programming 2 nd semester of 2017/2018 Credits: 5 Lecturer: Dr. Antoun Yaacoub 2 Multithreading

More information

Monitors & Condition Synchronization

Monitors & Condition Synchronization Feb. 15, 2012 Monitors & condition Synchronization Concepts: monitors: encapsulated data + access procedures mutual exclusion + condition synchronization single access procedure active in the monitor Models:

More information

Concurrency COMS W4115. Prof. Stephen A. Edwards Spring 2002 Columbia University Department of Computer Science

Concurrency COMS W4115. Prof. Stephen A. Edwards Spring 2002 Columbia University Department of Computer Science Concurrency COMS W4115 Prof. Stephen A. Edwards Spring 2002 Columbia University Department of Computer Science Concurrency Multiple, simultaneous execution contexts. Want to walk and chew gum at the same

More information

Implementing Coroutines. Faking Coroutines in Java

Implementing Coroutines. Faking Coroutines in Java Concurrency Coroutines Concurrency COMS W4115 Prof. Stephen A. Edwards Spring 2002 Columbia University Department of Computer Science Multiple, simultaneous execution contexts. Want to walk and chew gum

More information

CS193k, Stanford Handout #8. Threads 3

CS193k, Stanford Handout #8. Threads 3 CS193k, Stanford Handout #8 Spring, 2000-01 Nick Parlante Threads 3 t.join() Wait for finish We block until the receiver thread exits its run(). Use this to wait for another thread to finish. The current

More information

Chapter 6: Synchronization. Operating System Concepts 8 th Edition,

Chapter 6: Synchronization. Operating System Concepts 8 th Edition, Chapter 6: Synchronization, Silberschatz, Galvin and Gagne 2009 Outline Background The Critical-Section Problem Peterson s Solution Synchronization Hardware Semaphores Classic Problems of Synchronization

More information

Object Oriented Programming (II-Year CSE II-Sem-R09)

Object Oriented Programming (II-Year CSE II-Sem-R09) (II-Year CSE II-Sem-R09) Unit-VI Prepared By: A.SHARATH KUMAR M.Tech Asst. Professor JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY, HYDERABAD. (Kukatpally, Hyderabad) Multithreading A thread is a single sequential

More information

CMSC 433 Programming Language Technologies and Paradigms. Spring 2013

CMSC 433 Programming Language Technologies and Paradigms. Spring 2013 CMSC 433 Programming Language Technologies and Paradigms Spring 2013 Encapsulation, Publication, Escape Data Encapsulation One of the approaches in object-oriented programming is to use data encapsulation

More information

Concurrent and Real-Time Programming in Java

Concurrent and Real-Time Programming in Java 064202 Degree Examinations 2003 DEPARTMENT OF COMPUTER SCIENCE Concurrent and Real-Time Programming in Java Time allowed: One and one half (1.5) hours Candidates should answer not more than two questions.

More information

Unit III Rupali Sherekar 2017

Unit III Rupali Sherekar 2017 Unit III Exceptions An exception is an abnormal condition that arises in a code sequence at run time. In other words, an exception is a run-time error. In computer languages that do not support exception

More information

G52CON: Concepts of Concurrency

G52CON: Concepts of Concurrency G52CON: Concepts of Concurrency Lecture 11: Semaphores I" Brian Logan School of Computer Science bsl@cs.nott.ac.uk Outline of this lecture" problems with Peterson s algorithm semaphores implementing semaphores

More information

INF 212 ANALYSIS OF PROG. LANGS CONCURRENCY. Instructors: Crista Lopes Copyright Instructors.

INF 212 ANALYSIS OF PROG. LANGS CONCURRENCY. Instructors: Crista Lopes Copyright Instructors. INF 212 ANALYSIS OF PROG. LANGS CONCURRENCY Instructors: Crista Lopes Copyright Instructors. Basics Concurrent Programming More than one thing at a time Examples: Network server handling hundreds of clients

More information

Multi-threading in Java. Jeff HUANG

Multi-threading in Java. Jeff HUANG Multi-threading in Java Jeff HUANG Software Engineering Group @HKUST Do you use them? 2 Do u know their internals? 3 Let s see File DB How can they service so many clients simultaneously? l 4 Multi-threading

More information

Reading from URL. Intent - open URL get an input stream on the connection, and read from the input stream.

Reading from URL. Intent - open URL  get an input stream on the connection, and read from the input stream. Simple Networking Loading applets from the network. Applets are referenced in a HTML file. Java programs can use URLs to connect to and retrieve information over the network. Uniform Resource Locator (URL)

More information

Processes and Threads. Industrial Programming. Processes and Threads (cont'd) Processes and Threads (cont'd)

Processes and Threads. Industrial Programming. Processes and Threads (cont'd) Processes and Threads (cont'd) Processes and Threads Industrial Programming Lecture 5: C# Threading Introduction, Accessing Shared Resources Based on: An Introduction to programming with C# Threads By Andrew Birrell, Microsoft, 2005

More information

Synchronization Lecture 23 Fall 2017

Synchronization Lecture 23 Fall 2017 Synchronization Lecture 23 Fall 2017 Announcements A8 released today, Due: 11/21 Late deadline is after Thanksgiving You can use your A6/A7 solutions or ours A7 correctness scores have been posted Next

More information

Threads & Concurrency

Threads & Concurrency 2 Due date of A7 Due d About A5-A6 We have changed the due date of A7 Friday, 28 April. Threads & Concurrency But the last date to submit A7 remains the same: 29 April. We make the last date be 29 April

More information

Handouts. 1 Handout for today! Recap. Homework #2 feedback. Last Time. What did you think? HW3a: ThreadBank. Today. Small assignment.

Handouts. 1 Handout for today! Recap. Homework #2 feedback. Last Time. What did you think? HW3a: ThreadBank. Today. Small assignment. Handouts CS193J: Programming in Java Summer Quarter 2003 Lecture 10 Thread Interruption, Cooperation (wait/notify), Swing Thread, Threading conclusions 1 Handout for today! #21: Threading 3 #22: HW3a:

More information

Unit 4. Thread class & Runnable Interface. Inter Thread Communication

Unit 4. Thread class & Runnable Interface. Inter Thread Communication Unit 4 Thread class & Runnable Interface. Inter Thread Communication 1 Multithreaded Programming Java provides built-in support for multithreaded programming. A multithreaded program contains two or more

More information

Lecture 17: Sharing Objects in Java

Lecture 17: Sharing Objects in Java COMP 150-CCP Concurrent Programming Lecture 17: Sharing Objects in Java Dr. Richard S. Hall rickhall@cs.tufts.edu Concurrent programming March 25, 2008 Reference The content of this lecture is based on

More information

Threads and Locks, Part 2. CSCI 5828: Foundations of Software Engineering Lecture 08 09/18/2014

Threads and Locks, Part 2. CSCI 5828: Foundations of Software Engineering Lecture 08 09/18/2014 Threads and Locks, Part 2 CSCI 5828: Foundations of Software Engineering Lecture 08 09/18/2014 1 Goals Cover the material presented in Chapter 2 of our concurrency textbook In particular, selected material

More information

Outline of lecture. i219 Software Design Methodology 10. Multithreaded programming. Kazuhiro Ogata (JAIST)

Outline of lecture. i219 Software Design Methodology 10. Multithreaded programming. Kazuhiro Ogata (JAIST) i219 Software Design Methodology 10. Multithreaded programming Kazuhiro Ogata (JAIST) Outline of lecture 2 Thread Race condition Synchronization Deadlock Bounded buffer problem Thread (1) 3 Units of execution.

More information

Monitors & Condition Synchronization

Monitors & Condition Synchronization Chapter 5 Monitors & Condition Synchronization controller 1 Monitors & Condition Synchronization Concepts: monitors (and controllers): encapsulated data + access procedures + mutual exclusion + condition

More information

Systems Programming & Scripting

Systems Programming & Scripting Systems Programming & Scripting Lecture 10: C# Threading Introduction, Accessing Shared Resources Based on: An Introduction to programming with C# Threads By Andrew Birrell, Microsoft, 2005 Examples from

More information

Advanced Java Programming Course. MultiThreading. By Võ Văn Hải Faculty of Information Technologies Industrial University of Ho Chi Minh City

Advanced Java Programming Course. MultiThreading. By Võ Văn Hải Faculty of Information Technologies Industrial University of Ho Chi Minh City Advanced Java Programming Course MultiThreading By Võ Văn Hải Faculty of Information Technologies Industrial University of Ho Chi Minh City Session objectives Introduction Creating thread Thread class

More information

Unit - IV Multi-Threading

Unit - IV Multi-Threading Unit - IV Multi-Threading 1 Uni Processing In the early days of computer only one program will occupy the memory. The second program must be in waiting. The second program will be entered whenever first

More information

CSci 4061 Introduction to Operating Systems. Synchronization Basics: Locks

CSci 4061 Introduction to Operating Systems. Synchronization Basics: Locks CSci 4061 Introduction to Operating Systems Synchronization Basics: Locks Synchronization Outline Basics Locks Condition Variables Semaphores Basics Race condition: threads + shared data Outcome (data

More information

Concurrency Utilities: JSR-166

Concurrency Utilities: JSR-166 Concurrency Concurrency Utilities: JSR-166 Enables development of simple yet powerful multi-threaded applications > Like Collection provides rich data structure handling capability Beat C performance in

More information

Chapter 6: Process Synchronization

Chapter 6: Process Synchronization Chapter 6: Process Synchronization Objectives Introduce Concept of Critical-Section Problem Hardware and Software Solutions of Critical-Section Problem Concept of Atomic Transaction Operating Systems CS

More information

Concurrency & Parallelism. Threads, Concurrency, and Parallelism. Multicore Processors 11/7/17

Concurrency & Parallelism. Threads, Concurrency, and Parallelism. Multicore Processors 11/7/17 Concurrency & Parallelism So far, our programs have been sequential: they do one thing after another, one thing at a. Let s start writing programs that do more than one thing at at a. Threads, Concurrency,

More information

public class Shared0 { private static int x = 0, y = 0;

public class Shared0 { private static int x = 0, y = 0; A race condition occurs anytime that the execution of one thread interferes with the desired behavior of another thread. What is the expected postcondition for the following bump() method? What should

More information