Class ParallelSection
A group of parallel sections may be executed concurrently by calling a
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
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 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 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 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 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 IntegerForLoop, IntegerStrideForLoop, LongForLoop, and LongStrideForLoop for further information.
By calling a 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 ParallelIteration for further
information.
- Version:
- 11-Nov-2007
- Author:
- Alan Kaminsky
-
Constructor Summary
Constructors -
Method Summary
Methods inherited from class edu.rit.pj.ParallelConstruct
getThreadCount, getThreadIndex, isExecutingInParallel, region, team