Detailed Description

Class that implements the two heuristics to determine when a re-balance of the distribution is needed.

Used heuristics are: SAR and Un-balance Threshold (Default)
To chose the heuristic use the method setHeuristic(Heuristic)

In the SAR heuristic the following formula is applied:
\(W_{n} = \frac{\sum_{j=1}^{n} (T_{max}(j) - T_{avg}(j)) + C} {n}\)

\(T_{max}(j)\) – wall-clock time of bottleneck process in time step j
\(T_{avg}(j)\) – average wall-clock time for time step j over all processes
\(C\) – cost of re-decomposing the problem
\(n\) – number of time steps since last re-decomposition

For small n, load balance is good and W decreases since C is amortized over an increasing number of time steps. As the accumulated idle time starts to dominate, W starts to rise. At this point, C has been fully amortized. Re-decompose when \(W_{n} > W_{n-1}\)
In the Un-balance Threshold heuristic the re-balance is triggered when the un-balance level exceeds a certain level. Levels can be chosen in the ThresholdLevel type.

Definition at line 53 of file DLB.hpp.

#include <DLB.hpp>

Public Types
enum	Heuristic { SAR_HEURISTIC, UNBALANCE_THRLD }
	Type of DLB heuristics.

enum	ThresholdLevel { THRLD_LOW = 5, THRLD_MEDIUM = 7, THRLD_HIGH = 10 }
	Level of un-balance needed to trigger the re-balance.

Public Member Functions
	DLB (Vcluster &v_cl)
	Constructor for DLB class. More...

void	setHeurisitc (Heuristic h)
	Set the heuristic to use (default: un-balance threshold) More...

Heuristic	getHeurisitc ()
	Get the heuristic. More...

bool	rebalanceNeeded ()
	check if a re-balance is needed using the selected heuristic More...

void	setSimulationStartTime (size_t t)
	Set start time for the simulation. More...

size_t	getSimulationStartTime ()
	Get start time for the simulation. More...

void	setSimulationEndTime (size_t t)
	Set end time for the simulation. More...

size_t	getSimulationEndTime ()
	Get end time for the simulation. More...

void	startIteration ()
	Set start time for the single iteration. More...

void	startIteration (size_t t)
	Set start time for the single iteration. More...

void	endIteration ()
	Set end time for the single iteration. More...

void	endIteration (size_t t)
	Set the end time when the previous rebalance has been performed. More...

void	setTimeStep (double t)
	Set delta time step for one iteration (Computation time) More...

void	setComputationCost (size_t computation)
	Set time step for the single iteration. More...

size_t	getNTimeStepSinceDLB ()
	Get how many time-steps have passed since the last re-balancing. More...

void	setUnbalance (float u)
	Set un-balance value. More...

void	setThresholdLevel (ThresholdLevel t)
	threshold of umbalance to start a rebalance More...

Private Member Functions
bool	SAR ()
	Function that gather times informations and decides if a rebalance is needed it uses the SAR heuristic. More...

bool	unbalanceThreshold ()
	Check if the un-balance has exceeded the threshold. More...

Private Attributes
Vcluster &	v_cl
	Runtime virtual cluster machine.

Times	timeInfo
	Structure that will contain all the timings.

float	w_n = -1
	Wn for SAR heuristic.

float	c_c = 5
	Computation cost for SAR heuristic.

size_t	n_ts = 1
	Number of time-steps since the previous DLB.

float	i_time = 0
	Idle time accumulated so far, needed for SAR heuristic.

openfpm::vector< long >	times
	Vector to collect all timings.

Heuristic	heuristic = UNBALANCE_THRLD
	Type of the heuristic to use.

float	unbalance = -1
	Un-balance value.

ThresholdLevel	thl = THRLD_MEDIUM
	Threshold value.

Constructor & Destructor Documentation

DLB::DLB ( Vcluster & v_cl )

inline

Constructor for DLB class.

Parameters

v_cl	virtual cluster object

Definition at line 168 of file DLB.hpp.

Member Function Documentation

void DLB::endIteration ( )

inline

Set end time for the single iteration.

Parameters

time	when one iteration is completed

Definition at line 272 of file DLB.hpp.

void DLB::endIteration ( size_t t )

inline

Set the end time when the previous rebalance has been performed.

Parameters

t	time when one iteration ends

Definition at line 281 of file DLB.hpp.

Heuristic DLB::getHeurisitc ( )

inline

Get the heuristic.

Indicate which heuristic model is used to calculate when a rebalance is needed

Returns: the Heuristic used by DLB

Definition at line 190 of file DLB.hpp.

size_t DLB::getNTimeStepSinceDLB ( )

inline

Get how many time-steps have passed since the last re-balancing.

Returns: number of timesteos

Definition at line 309 of file DLB.hpp.

size_t DLB::getSimulationEndTime ( )

inline

Get end time for the simulation.

Returns: the end time of the simulation

Definition at line 245 of file DLB.hpp.

size_t DLB::getSimulationStartTime ( )

inline

Get start time for the simulation.

Returns: the start point of the simulation

Definition at line 226 of file DLB.hpp.

bool DLB::rebalanceNeeded ( )

inline

check if a re-balance is needed using the selected heuristic

Returns: true if the rebalance is needed

Definition at line 200 of file DLB.hpp.

bool DLB::SAR ( )

inlineprivate

Function that gather times informations and decides if a rebalance is needed it uses the SAR heuristic.

Returns: true if re-balance is needed

Definition at line 106 of file DLB.hpp.

void DLB::setComputationCost ( size_t computation )

inline

Set time step for the single iteration.

Parameters

computation value of the computation cost (default: 5)

Definition at line 299 of file DLB.hpp.

void DLB::setHeurisitc ( Heuristic h )

inline

Set the heuristic to use (default: un-balance threshold)

Parameters

h

Definition at line 177 of file DLB.hpp.

void DLB::setSimulationEndTime ( size_t t )

inline

Set end time for the simulation.

Parameters

t	time when the whole simulation ends

Definition at line 235 of file DLB.hpp.

void DLB::setSimulationStartTime ( size_t t )

inline

Set start time for the simulation.

Parameters

t	time when the whole simulation starts

Definition at line 216 of file DLB.hpp.

void DLB::setThresholdLevel ( ThresholdLevel t )

inline

threshold of umbalance to start a rebalance

Parameters

t	threshold level

Definition at line 327 of file DLB.hpp.

void DLB::setTimeStep ( double t )

inline

Set delta time step for one iteration (Computation time)

Parameters

t timestep

Definition at line 290 of file DLB.hpp.

void DLB::setUnbalance ( float u )

inline

Set un-balance value.

Parameters

u unbalance

Definition at line 318 of file DLB.hpp.

void DLB::startIteration ( )

inline

Set start time for the single iteration.

Definition at line 253 of file DLB.hpp.

void DLB::startIteration ( size_t t )

inline

Set start time for the single iteration.

Parameters

t	time when the one iteration starts

Definition at line 262 of file DLB.hpp.

bool DLB::unbalanceThreshold ( )

inlineprivate

Check if the un-balance has exceeded the threshold.

Returns: true if re-balance is needed, false otherwise

Definition at line 146 of file DLB.hpp.

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

src/DLB/DLB.hpp

Detailed Description

Public Types

Public Member Functions

Private Member Functions

Private Attributes

Constructor & Destructor Documentation

Member Function Documentation