tarch::timing::Measurement Class Reference

Measurement. More...

#include <Measurement.h>

Collaboration diagram for tarch::timing::Measurement:

Public Member Functions
	Measurement (const double &accuracy=0.0)
	~Measurement ()=default
double	getValue () const
double	getMostRecentValue () const
double	getAccumulatedValue () const
double	getStandardDeviation () const
	We did face some seg faults (very rarely) where the parameter under the square root did become slightly negative.
bool	isAccurateValue () const
	Is value accurate.
void	setAccuracy (const double &value)
void	increaseAccuracy (const double &factor)
void	setValue (const double &value)
	Set the value.
int	getNumberOfMeasurements () const
std::string	toString () const
double	max () const
double	min () const
void	erase ()
double	getAccuracy () const

Private Member Functions
double	getMeanValue () const
double	getMeanValueOfNextStep (double newValue) const

Private Attributes
double	_accuracy
double	_accumulatedValue
	Accumulated value.
double	_lastValue
	We store the last value.
double	_accumulatedSquares
	To compute the standard deviation, we rely on the formula.
double	_numberOfMeasurements
	Needed to compute average value and variance.
bool	_isAccurateValue
double	_min
double	_max
double	_minMeasurement
double	_maxMeasurement

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

Detailed Description

Measurement.

The shared memory oracles have to handle real time measurements. This data is always noisy, inaccurate, and has to be averaged. We originally planned to move all the averaging etc. to the oracle singleton. However, that is hardly possible, as the responsible oracle changes all the time, and the measurements are associated to one oracle. Consequently, we introduced this helper class for the individual oracle implementations.

Author

Tobias Weinzierl

Definition at line 29 of file Measurement.h.

Constructor & Destructor Documentation

Measurement()

tarch::timing::Measurement::Measurement

(

const double &

accuracy = 0.0

)

~Measurement()

tarch::timing::Measurement::~Measurement ( )

default

Member Function Documentation

erase()

void tarch::timing::Measurement::erase

(

)

getAccumulatedValue()

double tarch::timing::Measurement::getAccumulatedValue

(

)

const

Returns

Sum over all values measured so far.

getAccuracy()

double tarch::timing::Measurement::getAccuracy

(

)

const

getMeanValue()

double tarch::timing::Measurement::getMeanValue ( ) const

private

getMeanValueOfNextStep()

double tarch::timing::Measurement::getMeanValueOfNextStep ( double newValue ) const

private

getMostRecentValue()

double tarch::timing::Measurement::getMostRecentValue

(

)

const

Returns

Last value added. If there's none so far, the routine returns 0. If you've only added one value so far, the result equals getValue().

getNumberOfMeasurements()

int tarch::timing::Measurement::getNumberOfMeasurements

(

)

const

getStandardDeviation()

double tarch::timing::Measurement::getStandardDeviation

(

)

const

We did face some seg faults (very rarely) where the parameter under the square root did become slightly negative.

This seems to be a round-off error. We circumnavigate it by adding an absolute value which is mathematically not required.

getValue()

double tarch::timing::Measurement::getValue

(

)

const

Returns

Averaged value (mean value) of all measurements. If you have not yet added a value, it returns 0.

increaseAccuracy()

void tarch::timing::Measurement::increaseAccuracy

(

const double &

factor

)

isAccurateValue()

bool tarch::timing::Measurement::isAccurateValue

(

)

const

Is value accurate.

Whether a value is accurate depends on the last setValue() call. The class internally holds the mean value of all setValue() calls. If a new value is set/added, the object checks whether this additional measurement modifies the mean value more than the given accuracy. If this is the case, the object does not represent a valid measurement yet.

It does not work if we just compare new values to the mean value. If a measurement looks similar to the sketch from above (black=mean value, grey area=accuracy, blue points=values), the measurement never would become valid.

I therefore use a normalised mean value

\( valid = | \frac{ m^{(n+1)} - m^{(n)} }{m^{(n)}} | \leq \epsilon = | \frac{m^{(n+1)}}{m^{(n)}}-1 | \leq \epsilon \)

where \( m^{(n)} \) and \( m^{(n+1)} \) are two subsequent mean values.

max()

double tarch::timing::Measurement::max

(

)

const

min()

double tarch::timing::Measurement::min

(

)

const

setAccuracy()

void tarch::timing::Measurement::setAccuracy

(

const double &

value

)

See also

isAccurateValue()

setValue()

void tarch::timing::Measurement::setValue

(

const double &

value

)

Set the value.

If the measurement already holds a value, this value is not overwritten. Instead, the measurement accumulates all values and returns the average.

toString()

std::string tarch::timing::Measurement::toString

(

)

const

Field Documentation

_accumulatedSquares

double tarch::timing::Measurement::_accumulatedSquares

private

To compute the standard deviation, we rely on the formula.

sigma = sqrt(E(x^2) - E(x)^2)

with E being the mean value.

Definition at line 55 of file Measurement.h.

_accumulatedValue

double tarch::timing::Measurement::_accumulatedValue

private

Accumulated value.

The sum of all values divided by _numberOfMeasurements gives the mean value.

Definition at line 41 of file Measurement.h.

_accuracy

double tarch::timing::Measurement::_accuracy

private

Definition at line 33 of file Measurement.h.

_isAccurateValue

bool tarch::timing::Measurement::_isAccurateValue

private

Definition at line 61 of file Measurement.h.

_lastValue

double tarch::timing::Measurement::_lastValue

private

We store the last value.

Definition at line 46 of file Measurement.h.

_log

tarch::logging::Log tarch::timing::Measurement::_log

staticprivate

Definition at line 31 of file Measurement.h.

_max

double tarch::timing::Measurement::_max

private

Definition at line 63 of file Measurement.h.

_maxMeasurement

double tarch::timing::Measurement::_maxMeasurement

private

Definition at line 65 of file Measurement.h.

_min

double tarch::timing::Measurement::_min

private

Definition at line 62 of file Measurement.h.

_minMeasurement

double tarch::timing::Measurement::_minMeasurement

private

Definition at line 64 of file Measurement.h.

_numberOfMeasurements

double tarch::timing::Measurement::_numberOfMeasurements

private

Needed to compute average value and variance.

Definition at line 60 of file Measurement.h.

---

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

• src/tarch/timing/Measurement.h