org.cloudbus.cloudsim.utilizationmodels

Class UtilizationModelStochastic

java.lang.Object

org.cloudbus.cloudsim.utilizationmodels.UtilizationModelAbstract

org.cloudbus.cloudsim.utilizationmodels.UtilizationModelStochastic

All Implemented Interfaces:

UtilizationModel

public class UtilizationModelStochastic
extends UtilizationModelAbstract

Implements a model, according to which a Cloudlet generates random resource utilization every time frame.

Since:

CloudSim Toolkit 2.0

Author:

Anton Beloglazov, Manoel Campos da Silva Filho

Nested Class Summary

Nested classes/interfaces inherited from interface org.cloudbus.cloudsim.utilizationmodels.UtilizationModel

UtilizationModel.Unit

Field Summary

Fields inherited from class org.cloudbus.cloudsim.utilizationmodels.UtilizationModelAbstract

ALMOST_ZERO

Fields inherited from interface org.cloudbus.cloudsim.utilizationmodels.UtilizationModel

NULL

Constructor Summary

Constructors

Constructor and Description
UtilizationModelStochastic() Instantiates a new utilization model stochastic that defines the resource utilization in percentage.
UtilizationModelStochastic(ContinuousDistribution prng) Instantiates a new utilization model stochastic based on a given Pseudo Random Number Generator (PRNG) It defines the resource utilization in percentage.
UtilizationModelStochastic(UtilizationModel.Unit unit) Instantiates a new utilization model stochastic where the resource utilization is defined in the given unit.
UtilizationModelStochastic(UtilizationModel.Unit unit, ContinuousDistribution prng) Instantiates a new utilization model stochastic based on a given Pseudo Random Number Generator (PRNG).
UtilizationModelStochastic(UtilizationModel.Unit unit, long seed) Instantiates a new utilization model stochastic where the resource utilization is defined in the given unit.

Method Summary

Modifier and Type	Method and Description
UtilizationModelStochastic	disableHistory() Disables the resource utilization history, so that utilization values is NOT stored along all the simulation execution.
UtilizationModelStochastic	enableHistory() Enables the resource utilization history, so that utilization values is stored along all the simulation execution.
ContinuousDistribution	getRandomGenerator() Gets the random number generator.
double	getUtilization(double time) Gets the expected utilization of resource at a given simulation time.
protected Double	getUtilizationHistory(double time) Gets the utilization percentage for a given time from the internal historyMap.
boolean	isAlwaysGenerateNewRandomUtilization() Checks if every time the UtilizationModelAbstract.getUtilization() or getUtilization(double) methods are called, a new randomly generated utilization will be returned or not.
boolean	isHistoryEnabled() Checks if the history of resource utilization along simulation time is to be kept or not.
void	loadHistory(String filename) Load an utilization history from a file.
void	saveHistory(String filename) Save the utilization history to a file.
UtilizationModelStochastic	setAlwaysGenerateNewRandomUtilization(boolean alwaysGenerateNewRandomUtilization) Enables or disables the resource utilization history, so that utilization values is stored along all the simulation execution.
UtilizationModelStochastic	setHistoryEnabled(boolean enableHistory) Enables or disables the resource utilization history, so that utilization values is stored along all the simulation execution.
void	setRandomGenerator(ContinuousDistribution randomGenerator) Sets the random number generator.

Methods inherited from class org.cloudbus.cloudsim.utilizationmodels.UtilizationModelAbstract

getSimulation, getUnit, getUtilization, setSimulation, setUnit, validateUtilizationField, validateUtilizationField

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

UtilizationModelStochastic

public UtilizationModelStochastic()

Instantiates a new utilization model stochastic that defines the resource utilization in percentage. The resource utilization history is disabled by default.

See Also:

#setUnit(Unit), enableHistory(), isAlwaysGenerateNewRandomUtilization()

UtilizationModelStochastic

public UtilizationModelStochastic(UtilizationModel.Unit unit)

Instantiates a new utilization model stochastic where the resource utilization is defined in the given unit. The resource utilization history is disabled by default.

Parameters:

unit - the Unit that determines how the resource is used (for instance, if resource usage is defined in percentage of the Vm resource or in absolute values)

See Also:

enableHistory(), isAlwaysGenerateNewRandomUtilization()

UtilizationModelStochastic

public UtilizationModelStochastic(UtilizationModel.Unit unit,
                                  long seed)

Instantiates a new utilization model stochastic where the resource utilization is defined in the given unit. The resource utilization history is disabled by default.

Parameters:

unit - the Unit that determines how the resource is used (for instance, if resource usage is defined in percentage of the Vm resource or in absolute values)

seed - the seed to initialize the random number generator. If -1 is passed, the current time will be used.

See Also:

enableHistory(), isAlwaysGenerateNewRandomUtilization()

UtilizationModelStochastic

public UtilizationModelStochastic(ContinuousDistribution prng)

Instantiates a new utilization model stochastic based on a given Pseudo Random Number Generator (PRNG) It defines the resource utilization in percentage. The resource utilization history is disabled by default.

Parameters:

prng - the Pseudo Random Number Generator (PRNG) to generate utilization values

See Also:

#setUnit(Unit), enableHistory(), isAlwaysGenerateNewRandomUtilization()

UtilizationModelStochastic

public UtilizationModelStochastic(UtilizationModel.Unit unit,
                                  ContinuousDistribution prng)

Instantiates a new utilization model stochastic based on a given Pseudo Random Number Generator (PRNG). The resource utilization history is disabled by default.

Parameters:

unit - the Unit that determines how the resource is used (for instance, if resource usage is defined in percentage of the Vm resource or in absolute values)

prng - the Pseudo Random Number Generator (PRNG) to generate utilization values

See Also:

enableHistory(), isAlwaysGenerateNewRandomUtilization()

Method Detail

getUtilization

public double getUtilization(double time)

Gets the expected utilization of resource at a given simulation time. Such a value can be a percentage in scale from [0 to 1] or an absolute value, depending on the UtilizationModel.getUnit().

It is an expected usage value because the actual Cloudlet resource usage depends on the available Vm resource.

The method may return different utilization values for the same requested time. For performance reasons, this behaviour is dependent of the isHistoryEnabled() and isAlwaysGenerateNewRandomUtilization().

Parameters:

time - the time to get the resource usage.

Returns:

the resource utilization at the given time

See Also:

Issue #197 for more details

getUtilizationHistory

protected Double getUtilizationHistory(double time)

Gets the utilization percentage for a given time from the internal historyMap.

Parameters:

time - the time to get the utilization history for

Returns:

the stored utilization percentage or null if it has never been generated an utilization value for the given time

saveHistory

public void saveHistory(String filename)

Save the utilization history to a file.

Parameters:

filename - the filename

Throws:

UncheckedIOException - when the file cannot be accessed

loadHistory

public void loadHistory(String filename)

Load an utilization history from a file.

Parameters:

filename - the filename

Throws:

UncheckedIOException - when the file cannot be accessed

getRandomGenerator

public ContinuousDistribution getRandomGenerator()

Gets the random number generator.

Returns:

the random number generator

setRandomGenerator

public final void setRandomGenerator(ContinuousDistribution randomGenerator)

Sets the random number generator.

Parameters:

randomGenerator - the new random number generator

isHistoryEnabled

public boolean isHistoryEnabled()

Checks if the history of resource utilization along simulation time is to be kept or not.

Returns:

true if the history is to be kept, false otherwise

See Also:

enableHistory(), disableHistory()

setHistoryEnabled

public UtilizationModelStochastic setHistoryEnabled(boolean enableHistory)

Enables or disables the resource utilization history, so that utilization values is stored along all the simulation execution.

Parameters:

enableHistory - true to enable the utilization history, false to disable

Returns:

See Also:

enableHistory(), disableHistory()

enableHistory

public UtilizationModelStochastic enableHistory()

Enables the resource utilization history, so that utilization values is stored along all the simulation execution.

Returns:

disableHistory

public UtilizationModelStochastic disableHistory()

Disables the resource utilization history, so that utilization values is NOT stored along all the simulation execution.

Returns:

isAlwaysGenerateNewRandomUtilization

public boolean isAlwaysGenerateNewRandomUtilization()

Checks if every time the UtilizationModelAbstract.getUtilization() or getUtilization(double) methods are called, a new randomly generated utilization will be returned or not. This attribute is false by default, meaning that consecutive utilization requests for the same time may return the same previous generated utilization value. Check the documentation in the return section at the end for details.

Using one instance of this utilization model for every Cloudlet in a large simulation scenario may be very expensive in terms of simulation time and memory consumption. This way, the researcher may want to use a single utilization model instance for every Cloudlet. The side effect is that, if this attribute is false (the default), it will usually return the same utilization value for the same requested time for distinct Cloudlets. That commonly is not what the researcher wants. He/she usually wants that every Cloudlet has an independent resource utilization.

To reduce simulation time and memory consumption, you can use a single utilization model instance for a given Cloudlet resource (such as CPU) and set this attribute to false. This way, it will always generate different utilization values for every time an utilization is requested (even if the same previous time is given).

Returns:

true if a new randomly generated utilization will always be returned; false if for the same requested time, the same utilization must be returned. In this last case, it's just ensured that, for a given time, the same utilization will always be returned, if the history is enabled.

See Also:

setAlwaysGenerateNewRandomUtilization(boolean)

setAlwaysGenerateNewRandomUtilization

public UtilizationModelStochastic setAlwaysGenerateNewRandomUtilization(boolean alwaysGenerateNewRandomUtilization)

Enables or disables the resource utilization history, so that utilization values is stored along all the simulation execution.

Parameters:

alwaysGenerateNewRandomUtilization - true to enable the utilization history, false to disable

Returns:

See Also:

isAlwaysGenerateNewRandomUtilization()