Concurrencyproblem

Concurrency Problem
Adriano Patrick Cunha - UDCE

quarta-feira, 10 de outubro de 2012

Evolution of processors


Big Data to process


What Possibilities ?


Concurrence?


Which options ?


Functional Programming language ?


API java.util.concurrent

5

Thead-Safe


Thead-Safe

private
Set<String>
ipAddressSet
=
new
HashSet<String>();


Thead-Safe

private
Set<String>
ipAddressSet
=
new
HashSet<String>();

private
Set<String>
ipAddressSet
=
Collections.

synchonizedSet(new
HashSet<String>());


Thead-Safe

private
Set<String>
ipAddressSet
=
new
HashSet<String>();

private
Set<String>
ipAddressSet
=
Collections.

synchonizedSet(new
HashSet<String>());
private
BlockingQueue<String>
ipAddress=new
LinkedBlockingQueue<String>();


Thead-Safe

fast-fail iterators
private
Set<String>
ipAddressSet
=
new
HashSet<String>();

private
Set<String>
ipAddressSet
=
Collections.

synchonizedSet(new
HashSet<String>());
private
BlockingQueue<String>
ipAddress=new
LinkedBlockingQueue<String>();

weakly consistent iterators


Thead-Safe

Outras
Coleções

ConcurrentHashMap,
CopyOnWriteArrayList
e

CopyOnWriteArraySet


Executor

Executor
ExecutorService
ScheduledExecutorService


Executor

(new Thread(r)).start();


Executor

(new Thread(r)).start();
e.execute(r);


Thread Pools

Executors.newCachedThreadPool();

Executors.newFixedThreadPoll(n);

Executors.newSingleThreadExecutor();


Thread Pools
class Counter {
private int c = 0;

public void increment() {
c++;
}

public void decrement() {
c--;
}

public int value() {
return c;
}

}
1. Thread A: Retrieve c.
2. Thread B: Retrieve c.
1. Retrieve the current value of c.
3. Thread A: Increment retrieved value; result is 1.
2. Increment the retrieved value by 1.
4. Thread B: Decrement retrieved value; result is -1.
3. Store the incremented value back in c.
5. Thread A: Store result in c; c is now 1.
6. Thread B: Store result in c; c is now -1.


Thread Pools

class SynchronizedCounter {
private int c = 0;

public synchronized void increment() {
c++;
}

public synchronized void decrement() {
c--;
}

public synchronized int value() {
return c;
}

}


Thread Pools
import java.util.concurrent.atomic.AtomicInteger;

class AtomicCounter {
private AtomicInteger c = new AtomicInteger(0);

public void increment() {
c.incrementAndGet();
}

public void decrement() {
c.decrementAndGet();
}

public int value() {
return c.get();
}

}


Bibliograﬁa

Livros

Concurrent Programming in Java, Design Principles and Patterns, Doug Lea, Addison-Wesley, 1999

Java Concurrency In Practice, Brian Goetz, Addison-Wesley, 2006

Links

http://docs.oracle.com/javase/tutorial/essential/concurrency/index.html

http://www.jcp.org/en/jsr/detail?id=166

http://gee.cs.oswego.edu/dl/concurrency-interest/

http://www.devmedia.com.br/websys.2/webreader.asp?cat=6&revista=javamagazine_69


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