tarch::multicore::TaskEnumerator Class Reference

Rank-global enumerator for tasks. More...

#include <TaskEnumerator.h>

Inheritance diagram for tarch::multicore::TaskEnumerator:

Collaboration diagram for tarch::multicore::TaskEnumerator:

Public Member Functions
	TaskEnumerator ()
void	reset ()
int	getNumber ()
	Get a new task number.
void	releaseNumber (int value)
	Release a task number.
int	size () const
	Number of numbers handed out so far.
std::string	toString () const

Static Public Attributes
static constexpr int	NoNumber = -1

Static Private Member Functions
static tarch::multicore::MultiReadSingleWriteSemaphore &	_enumeratorSequenceSemaphore ()
	We use a method instead of a member variable so that thhe static semaphore is is guaranteed to be initialised before we use it.

Private Attributes
int	_enumeratorNumber
	Number of enumerator that's tied to this instance.

Static Private Attributes
static std::vector< tarch::Enumerator * >	_enumerator
static tarch::logging::Log	_log

Detailed Description

Rank-global enumerator for tasks.

The "problem" with tasks is that we often have different solvers running in parallel which all need their own task numbers. And these should, obviously, not conflict. The present enumerator tackles this problem:

The class is a wrapper layer around a set of enumerators. It is aware of the maximum number of tasks that our system can handle. Every time you construct an instance of this class, it coordinates internally with all the other instances of this class and ensures that each instance only hands out numbers from its specific range.

If you had, for example, only numbers from 0 up to 10000-1, and you create two instances of tarch::multicore::TaskEnumerator, then the first instance would only hand out numbers from 0 to 5000-1, and the second one only from 5000 to 10000-1. They ensure that there is no conflict.

The actual task number administration is thread-safe, as we rely internally on tarch::Enumerator instances on the heap. However, the creation of these heap objects can lead to race conditions. Therefore, we protect this access explicitly with a semaphore allowing for multiple reads but only one write.

Definition at line 41 of file TaskEnumerator.h.

Constructor & Destructor Documentation

TaskEnumerator()

tarch::multicore::TaskEnumerator::TaskEnumerator

(

)

Member Function Documentation

_enumeratorSequenceSemaphore()

static tarch::multicore::MultiReadSingleWriteSemaphore & tarch::multicore::TaskEnumerator::_enumeratorSequenceSemaphore ( )

staticprivate

We use a method instead of a member variable so that thhe static semaphore is is guaranteed to be initialised before we use it.

Without this we fall victim to the static initialisation order fiasco.

getNumber()

int tarch::multicore::TaskEnumerator::getNumber

(

)

Get a new task number.

Returns a unique non-zero number which is not yet used anywhere else on this rank. The function delegates the call to an instance of tarch::Enumerator::getNumber(). Consequently, it is thread-safe.

Returns

Non-zero number or tarch::Enumerator::NoNumber if there's no number left.

releaseNumber()

void tarch::multicore::TaskEnumerator::releaseNumber

(

int

value

)

Release a task number.

Free a number again. number has to be the result of a previous getNumber() call. Is thread-safe.

reset()

void tarch::multicore::TaskEnumerator::reset

(

)

size()

int tarch::multicore::TaskEnumerator::size

(

)

const

Number of numbers handed out so far.

Referenced by tarch.plotter.api.input.Patch.Patch::__repr__().

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toString()

std::string tarch::multicore::TaskEnumerator::toString

(

)

const

Field Documentation

_enumerator

std::vector< tarch::Enumerator* > tarch::multicore::TaskEnumerator::_enumerator

staticprivate

Definition at line 82 of file TaskEnumerator.h.

_enumeratorNumber

int tarch::multicore::TaskEnumerator::_enumeratorNumber

private

Number of enumerator that's tied to this instance.

The value serves as index to access _enumerator.

Logically, this attribute is a const attribute. We however cannot make it const, as the constructor first of all has to lock the array _enumerator, then it can determine what the value of _enumeratorNumber number is.

Definition at line 95 of file TaskEnumerator.h.

_log

tarch::logging::Log tarch::multicore::TaskEnumerator::_log

staticprivate

Definition at line 83 of file TaskEnumerator.h.

NoNumber

constexpr int tarch::multicore::TaskEnumerator::NoNumber = -1

staticconstexpr

Definition at line 43 of file TaskEnumerator.h.

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

• src/tarch/multicore/TaskEnumerator.h