SimTK::Parallel2DExecutor Class Reference

This class is used for performing multithreaded computations over two dimensional ranges. More...

#include <Parallel2DExecutor.h>

Inheritance diagram for SimTK::Parallel2DExecutor:

List of all members.

Classes
class	Task
	Concrete subclasses of this abstract class represent tasks that can be executed by a Parallel2DExecutor. More...
Public Types
enum	RangeType { FullMatrix, HalfMatrix, HalfPlusDiagonal }
Public Member Functions
	Parallel2DExecutor (int gridSize, int numThreads=ParallelExecutor::getNumProcessors())
	Construct a Parallel2DExecutor.
	Parallel2DExecutor (int gridSize, ParallelExecutor &executor)
	Construct a Parallel2DExecutor.
void	execute (Task &task, RangeType rangeType)
	Execute a parallel task.
ParallelExecutor &	getExecutor ()
	Get the ParallelExecutor used by this object to parallelize calculations.

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Detailed Description

This class is used for performing multithreaded computations over two dimensional ranges.

That is, it performs some calculation once for each pair (i, j) where i and j vary over some range. For example, it is useful for calculating pairwise forces between a set of bodies.

To use it, define a subclass of Parallel2DExecutor::Task that performs a computation. Then create a Parallel2DExecutor object and ask it to execute the task:

 Parallel2DExecutor executor(gridSize);
 executor.execute(myTask, Parallel2DExecutor::FullMatrix);
 

The Task's execute() method will be called once with each pair (i, j) where i and j vary between 0 and gridSize-1. You also can restrict it to only pairs with i > j or i >= j.

The invocations are done in parallel on multiple threads, but they are divided up in a way that avoids index conflicts between simultaneous calculations. If the task is executed with indices (i1, j1) on one thread, it is guaranteed that no other thread is simultaneously executing the task with either the first or second index equal to either i1 or j1. (More precisely, if either index of one invocation is equal to either index of another invocation, the two invocations are guaranteed to be separated by a happens-before edge.) This allows the task to modify data that is indexed by i and j without needing to worry about concurrent modifications.

The threads are created in the Parallel2DExecutor's constructor and remain active until it is deleted. This means that creating a Parallel2DExecutor is a somewhat expensive operation, but it may then be used repeatedly for executing various calculations. By default, the number of threads is chosen to be equal to the number of available processor cores. You can optionally specify a different number of threads to create. For example, using more threads than processors can sometimes lead to better processor utilitization.

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Member Enumeration Documentation

enum SimTK::Parallel2DExecutor::RangeType

Enumerator:

FullMatrix
HalfMatrix
HalfPlusDiagonal

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Constructor & Destructor Documentation

SimTK::Parallel2DExecutor::Parallel2DExecutor	(	int	gridSize,
		int	numThreads = ParallelExecutor::getNumProcessors()
	)		[explicit]

Construct a Parallel2DExecutor.

Parameters:

gridSize	the size of the range over which i and j should vary
numThreads	the number of threads to create. By default, this is set equal to the number of processors.

SimTK::Parallel2DExecutor::Parallel2DExecutor	(	int	gridSize,
		ParallelExecutor &	executor
	)

Construct a Parallel2DExecutor.

This constructor allows you to specify an existing ParallelExecutor to use for parallelizing the calculation. This can improve efficiency by reusing an existing thread pool. It is your responsibility to make sure that the ParallelExecutor does not get deleted as long as this object exists.

Parameters:

gridSize	the size of the range over which i and j should vary
executor	the ParallelExecutor to use for parallelizing calculations

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Member Function Documentation

void SimTK::Parallel2DExecutor::execute	(	Task &	task,
		RangeType	rangeType
	)

Execute a parallel task.

Parameters:

task	the Task to execute
rangeType	specifies what part of the range i and j should vary over. Specify FullyMatrix to execute the task for all values of i and j between 0 and gridSize, HalfMatrix to restrict it to i > j, and HalfPlusDiagonal to restrict it to i >= j.

ParallelExecutor& SimTK::Parallel2DExecutor::getExecutor

(

)

Get the ParallelExecutor used by this object to parallelize calculations.

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The documentation for this class was generated from the following file:

• Parallel2DExecutor.h