* A group of parallel sections may be executed concurrently by calling a * {@linkplain ParallelRegion}'s execute() method. Each section in the * group is executed by a different thread in the parallel thread team. Here is * one way to code a parallel section group with two parallel sections: *
* new ParallelTeam(2).execute (new ParallelRegion()
* {
* public void run() throws Exception
* {
* execute
* (new ParallelSection()
* {
* public void run()
* {
* // Code for first concurrent parallel section
* . . .
* }
* },
* new ParallelSection()
* {
* public void run()
* {
* // Code for second concurrent parallel section
* . . .
* }
* });
* }
* });
*
* Here is another way to code a parallel section group with two parallel
* sections:
*
* ParallelSection section_1 = new ParallelSection()
* {
* public void run()
* {
* // Code for first concurrent parallel section
* . . .
* }
* };
* ParallelSection section_2 = new ParallelSection()
* {
* public void run()
* {
* // Code for second concurrent parallel section
* . . .
* }
* };
* new ParallelTeam(2).execute (new ParallelRegion()
* {
* public void run() throws Exception
* {
* execute (section_1, section_2);
* }
* });
*
* A parallel section group may contain any number of parallel sections. There
* are overloaded execute() methods that take one, two, or three
* parallel section arguments. If there are four or more parallel sections, put
* them in an array (type ParallelSection[]) and pass the array to the
* execute() method.
* * Normally, at the end of the parallel section group, the parallel team threads * wait for each other at a barrier. To eliminate this barrier wait, include * {@link BarrierAction#NO_WAIT BarrierAction.NO_WAIT} in the execute() * method call: *
* new ParallelTeam(2).execute (new ParallelRegion()
* {
* public void run() throws Exception
* {
* execute (section_1, section_2, BarrierAction.NO_WAIT);
* }
* });
*
* To execute a section of code in a single thread as part of the barrier
* synchronization, include an instance of class {@linkplain BarrierAction} in
* the execute() method call. The barrier action object's
* run() method contains the code to be executed in a single thread
* while the other threads wait:
*
* new ParallelTeam(2).execute (new ParallelRegion()
* {
* public void run() throws Exception
* {
* execute (section_1, section_2, new BarrierAction()
* {
* public void run()
* {
* // Single-threaded code goes here
* . . .
* }
* });
* }
* });
*
* For further information, see class {@linkplain BarrierAction}.
* * A parallel section may be executed by one thread in the parallel thread team * by executing a parallel section group consisting of the one parallel section, * as shown above: *
* new ParallelTeam().execute (new ParallelRegion()
* {
* public void run() throws Exception
* {
* . . .
* execute (new ParallelSection()
* {
* public void run()
* {
* // Code to be executed by one parallel team thread
* . . .
* }
* });
* . . .
* }
* });
*
* * A parallel section may be executed in a mutually exclusive fashion by calling * a {@linkplain ParallelRegion}'s critical() or * criticalNonexclusive() method. For example: *
* new ParallelTeam().execute (new ParallelRegion()
* {
* public void run() throws Exception
* {
* . . .
* critical (new ParallelSection()
* {
* public void run()
* {
* // Mutually exclusive code
* . . .
* }
* });
* . . .
* }
* });
*
* * By calling a {@linkplain ParallelForLoop}'s ordered() method, a * parallel section may be executed in the order of the loop indexes within a * parallel for loop body, while the rest of the parallel for loop body executes * concurrently. See classes {@linkplain IntegerForLoop}, {@linkplain * IntegerStrideForLoop}, {@linkplain LongForLoop}, and {@linkplain * LongStrideForLoop} for further information. *
* By calling a {@linkplain ParallelIteration}'s ordered() method, a * parallel section may be executed in the order of the items within a parallel * iteration body, while the rest of the parallel iteration body executes * concurrently. See class {@linkplain ParallelIteration} for further * information. * * @author Alan Kaminsky * @version 11-Nov-2007 */ public abstract class ParallelSection extends ParallelConstruct { // Exported constructors. /** * Construct a new parallel section. */ public ParallelSection() { super(); } // Exported operations. /** * Execute this parallel section. *
* The run() method must be implemented in a subclass. * * @exception Exception * The run() method may throw any exception. */ public abstract void run() throws Exception; }