org.knowceans.topics.cgen
Class ParallelFor

java.lang.Object
  org.knowceans.topics.cgen.ParallelFor

public abstract class ParallelFor
extends java.lang.Object

ParallelFor implements what in OpenMP is called a parallel for loop, i.e., a loop that executes in parallel on several threads with a barrier (join) at the end. Implementors simply subclass and implement the process() method and make sure the loop() method is not called while a loop of one instance is running. Execution can be stopped using stop(), which completes the iterations currently running. After the last usage of the class, it should be shut down properly using function shutdown() or the hard way using System.exit();

Author:

Gregor Heinrich, semaphore approach by Bernd Amend

Field Summary

protected boolean	isStopping stop flag
protected java.util.concurrent.atomic.AtomicInteger	iteration current item index
protected int	nthreads number of threads = number of processors / cores
(package private) static long	start
(package private) static java.util.concurrent.atomic.AtomicInteger	test
protected java.util.concurrent.ExecutorService	threadpool pool of threads spread over processors

Constructor Summary

ParallelFor()
instantiate with as many threads as there are processors and block-wise execution

ParallelFor(int nthreads)
number of threads and mode: 1 = serial, negative = element-wise, positive = block-wise execution

Method Summary

void	loop(int range) Loop through all iterations.
void	loopOnce(int N) loops once, then shuts down
static void	main(java.lang.String[] args)
abstract void	process(int iteration, int thread) processing method
void	shutdown() shut down the thread pool after final usage
void	stop() stop loop execution

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

nthreads

protected int nthreads

number of threads = number of processors / cores

iteration

protected java.util.concurrent.atomic.AtomicInteger iteration

current item index

threadpool

protected java.util.concurrent.ExecutorService threadpool

pool of threads spread over processors

isStopping

protected boolean isStopping

stop flag

test

static java.util.concurrent.atomic.AtomicInteger test

start

static long start

Constructor Detail

ParallelFor

public ParallelFor()

instantiate with as many threads as there are processors and block-wise execution

ParallelFor

public ParallelFor(int nthreads)

number of threads and mode: 1 = serial, negative = element-wise, positive = block-wise execution

Parameters:

nthreads -

Method Detail

loop

public void loop(int range)

Loop through all iterations. Should never be called while the loop instance is still running.

Parameters:

range -

shutdown

public void shutdown()

shut down the thread pool after final usage

loopOnce

public void loopOnce(int N)
              throws java.lang.InterruptedException

loops once, then shuts down

Parameters:

N -

Throws:

java.lang.InterruptedException

stop

public void stop()

stop loop execution

process

public abstract void process(int iteration,
                             int thread)

processing method

Parameters:

iteration -

thread -

main

public static void main(java.lang.String[] args)
                 throws java.lang.InterruptedException

Throws:

java.lang.InterruptedException