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ExaHyPE 2-specific load balancing configuration. More...

#include <LoadBalancingConfiguration.h>

Inheritance diagram for exahype2::LoadBalancingConfiguration:

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Collaboration diagram for exahype2::LoadBalancingConfiguration:

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Public Member Functions
	LoadBalancingConfiguration (double loadBalancingQuality=0.9, int minSizeOfTree=0, bool assumePeriodicBoundaryConditions=false, int maxNumberOfTreesThroughoutInitialDistribution=UseNumberOfThreads, int maxNumberOfTrees=UseTwiceTheNumberOfThreads, peano4::SplitInstruction::Mode mode=peano4::SplitInstruction::Mode::BottomUp)
	Configure load balancing.

virtual	~LoadBalancingConfiguration ()=default

virtual bool	makeSplitDependOnMemory (toolbox::loadbalancing::State state) override
	Use the operating system's memory queries to get the memory out and to veto too many local splits.

virtual int	getMaxLocalTreesPerRank (toolbox::loadbalancing::State state) override
	Constraint on the number of trees per rank.

virtual double	getWorstCaseBalancingRatio (toolbox::loadbalancing::State state) override
	Control when to balance between ranks.

virtual int	getMinTreeSize (toolbox::loadbalancing::State state) override
	If we do the initial distribution in-between ranks, then there should be no such thing as a min tree size.

virtual std::string	toString () const override

virtual peano4::SplitInstruction::Mode	getMode (toolbox::loadbalancing::State state) override

Public Member Functions inherited from toolbox::loadbalancing::Configuration
virtual	~Configuration ()=default

Static Public Attributes
static constexpr int	UseNumberOfThreads = -1

static constexpr int	UseTwiceTheNumberOfThreads = -2

Private Member Functions
int	translateSetMaxNumberOfTreesIntoRealNumberOfTrees (int value) const
	Return how many trees to use if value is picked by user.

Private Attributes
const double	_loadBalancingQuality

const int	_minSizeOfTree

const bool	_assumePeriodicBoundaryConditions

const int	_maxNumberOfTreesThroughoutInitialDistribution

const int	_maxNumberOfTrees

const peano4::SplitInstruction::Mode	_mode

Static Private Attributes
static tarch::logging::Log	_log

Detailed Description

ExaHyPE 2-specific load balancing configuration.

Definition at line 19 of file LoadBalancingConfiguration.h.

Constructor & Destructor Documentation

◆ LoadBalancingConfiguration()

exahype2::LoadBalancingConfiguration::LoadBalancingConfiguration	(	double	loadBalancingQuality = 0.9,
		int	minSizeOfTree = 0,
		bool	assumePeriodicBoundaryConditions = false,
		int	maxNumberOfTreesThroughoutInitialDistribution = UseNumberOfThreads,
		int	maxNumberOfTrees = UseTwiceTheNumberOfThreads,
		peano4::SplitInstruction::Mode	mode = peano4::SplitInstruction::Mode::BottomUp )

Configure load balancing.

Parameters

minSizeOfTree If a partition (tree) is smaller than the given number of cells, we do not split it up further. If you set this argument to 0, you effectively set no threshold - Peano will try to split any tree if it thinks it would improve the load balancing.

This value is not taken into account for the initial distribution. Here, you have to use maxNumberOfTreesThroughoutInitialDistribution to constrain over-ambitious domain splitting.

Parameters

maxNumberOfTreesThroughoutInitialDistribution Set the maximum number of trees (per rank) that we use when we split up the domain no a rank for the first time. By default, I try to give each thread per rank exactly one subpartition to work on. You might want to reduce this value.

maxNumberOfTrees This value is used after the initial decomposition. If you pick it higher than maxNumberOfTreesThroughoutInitialDistribution, then you give the load balancing the opportunity to split up the domain further even if all threads have already one subpartition. I recommend to to pick it higher than maxNumberOfTreesThroughoutInitialDistribution, as the load balancer kicks in throughout the grid construction. By the time is uses maxNumberOfTreesThroughoutInitialDistribution threads, local adaptivity might not yet be established, i.e. subsequent grid refinements will yield imbalances that only further splits can compensate.

◆ ~LoadBalancingConfiguration()

virtual exahype2::LoadBalancingConfiguration::~LoadBalancingConfiguration ( )

virtualdefault

Member Function Documentation

◆ getMaxLocalTreesPerRank()

virtual int exahype2::LoadBalancingConfiguration::getMaxLocalTreesPerRank ( toolbox::loadbalancing::State state )

overridevirtual

Constraint on the number of trees per rank.

The number is always constrained by peano4::parallel::Node::MaxSpacetreesPerRank, but you can cut it down further.

You can use an arbitary large value if you don't care bout a maximum number of subpartitions per rank. I however do recommend that you return peano4::parallel::Node::MaxSpacetreesPerRank.

Implements toolbox::loadbalancing::Configuration.

◆ getMinTreeSize()

virtual int exahype2::LoadBalancingConfiguration::getMinTreeSize ( toolbox::loadbalancing::State state )

overridevirtual

If we do the initial distribution in-between ranks, then there should be no such thing as a min tree size.

Implements toolbox::loadbalancing::Configuration.

◆ getMode()

virtual peano4::SplitInstruction::Mode exahype2::LoadBalancingConfiguration::getMode ( toolbox::loadbalancing::State state )

overridevirtual

Implements toolbox::loadbalancing::Configuration.

◆ getWorstCaseBalancingRatio()

virtual double exahype2::LoadBalancingConfiguration::getWorstCaseBalancingRatio ( toolbox::loadbalancing::State state )

overridevirtual

Control when to balance between ranks.

Implements toolbox::loadbalancing::Configuration.

◆ makeSplitDependOnMemory()

virtual bool exahype2::LoadBalancingConfiguration::makeSplitDependOnMemory ( toolbox::loadbalancing::State state )

overridevirtual

Use the operating system's memory queries to get the memory out and to veto too many local splits.

Each split creates some overhead, so it can happen that we run out of memory.

Implements toolbox::loadbalancing::Configuration.

◆ toString()

virtual std::string exahype2::LoadBalancingConfiguration::toString ( ) const

overridevirtual

Reimplemented from toolbox::loadbalancing::Configuration.

◆ translateSetMaxNumberOfTreesIntoRealNumberOfTrees()

int exahype2::LoadBalancingConfiguration::translateSetMaxNumberOfTreesIntoRealNumberOfTrees ( int value ) const

private

Return how many trees to use if value is picked by user.

If the users sets a real number >0 for the upper number of trees, then we pick this value. However, if the users picks a magic constant, then we have to read out the real system configuration and translate it into a real number, i.e. if the user has picked UseNumberOfThreads for example, then we have to ask the core how many threads we really have and return that value.