ParallelOptions Class Reference

Option base class for parallel algorithms. More...

#include <vigra/threadpool.hxx>

Inheritance diagram for ParallelOptions:

Public Types
enum	{ Auto = -1 , Nice = -2 , NoThreads = 0 }

Public Member Functions
int	getActualNumThreads () const
	Get desired number of threads.
int	getNumThreads () const
	Get desired number of threads.
ParallelOptions &	numThreads (const int n)
	Set the number of threads or one of the constants Auto, Nice and NoThreads.

Detailed Description

Option base class for parallel algorithms.

#include <vigra/threadpool.hxx>
Namespace: vigra

Member Enumeration Documentation

anonymous enum

anonymous enum

Constants for special settings.

Enumerator
Auto	Determine number of threads automatically (from threading::thread::hardware_concurrency()).
Nice	Use half as many threads as Auto would.
NoThreads	Switch off multi-threading (i.e. execute tasks sequentially).

Member Function Documentation

getNumThreads()

int getNumThreads

(

)

const

Get desired number of threads.

Note: This function may return 0, which means that multi-threading shall be switched off entirely. If an algorithm receives this value, it should revert to a sequential implementation. In contrast, if numThread() == 1, the parallel algorithm version shall be executed with a single thread.

getActualNumThreads()

int getActualNumThreads

(

)

const

Get desired number of threads.

In contrast to numThread(), this will always return a value >=1.

numThreads()

ParallelOptions & numThreads

(

const int

n

)

Set the number of threads or one of the constants Auto, Nice and NoThreads.

Default: ParallelOptions::Auto (use system default)

This setting is ignored if the preprocessor flag VIGRA_SINGLE_THREADED is defined. Then, the number of threads is set to 0 and all tasks revert to sequential algorithm implementations. The same can be achieved at runtime by passing n = 0 to this function. In contrast, passing n = 1 causes the parallel algorithm versions to be executed with a single thread. Both possibilities are mainly useful for debugging.

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

• vigra/threadpool.hxx