Statistics

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Block Name: Statistics

Code File Location: VisualSim/actor/lib/Stats_Basic

Block Overview

  o  Compile the statistics for a sequence of scalar values- integer, double or long. For example, the input can be the current throughput.  The output at the end of the simulation can show the range of the throughput during the period of the simulation.  Similar experiments can be performed on latency, data size, read/write memory etc.

Description

This block collects data arriving on the input and continuously computes the statistics.  

This statistics block can sample every Nth data input. If the user wishes to collect the maximum statistical information, then one would set the 'Sample_Every_Nth_DS' parameter to 1 (default).

The 'Batch_Count_Min_Max' parameter is normally set to 1 0.0 100.0, where the first number indicates the number of batches (1), the second number indicates the start time (0.0), the last number indicates the stop time (100.0). The stop time can also be set to 'tstop', which will be interpreted by the block to insert the end of the simulation time. 

The "Statistics_Name" field is printed in the BLOCK field of the output data structure.

When the stats_trigger port is triggered, current values of the statistics are reported on the stats_out output port.  When the stats_reset input port is triggered, all statistics in the block is reset.  Both these ports can be fired at any time during the simulation.  The Histo port will output the histogram of the sequence values- X-axis will be the value and Y-axis will be the number of occurances of each column.

Refer Statistics Demo Model.


Statistic Name

Explanation

Mathematical Equation

Sample Values

 Type 

Statistic_Name

Unique name to identify the output. Added to the field called Statistics_Name in the output data structure.

-

Queue_Length

String

Number_Values

Number of entries to this block and used to calculate the statistics.

-

2513

int

Min_Value

Minimum queue size during the simulation. (Value opposed to time delay or occupancy).

// Obtain Min for X, where X0 = Double.MAX_VALUE

 if (Xn < Xn – 1) Xmin = Xn

0.0

double

Mean_Value

Mean/Average queue size during the simulation (Value opposed to time delay or occupancy).

 // Obtain Mean for X

    Xµ  = (1 / n) * (X1 + X2 + … + Xn)

1.112216474333466

double

StDev_Value

Standard Deviation from the Mean queue size during the simulation.(Value opposed to time delay or occupancy).

// Obtain Standard Deviation for X
 Xσ = Math.sqrt ((1 / n) * ((X1 - Xµ)2 + (X2 - Xµ)2  + … + (Xn - Xµ)2))

STDEV_90_PCT = 1.6448530004790

STDEV_95_PCT = 1.9599610823207

STDEV_99_PCT = 2.5758345145732

0.8256330697465197

double

Max_Value

Maximum queue size consumed during the simulation. (Value opposed to time delay or occupancy).

// Obtain Max for X, where X0 = Double.MIN_VALUE             

    if (Xn > Xn – 1) Xmax = Xn

4.0

double

Mean_95_Confidence

The 95% confidence intervals is used to indicate the reliability of an estimate. How likely the interval is to contain the parameter is determined by the confidence level or confidence coefficient. The confidence level is 95%.

// Obtain 95% Confidence Interval for Mean.

Xµ95  = STDEV_95_PCT * (Xσ / Math.sqrt(n)))  

0.0322803536050639

double

Data_95_StDev_196s

This is the standard deviation of the confidence interval.

// Obtain 95% Confidence Interval for Mean.

Xµ95  = STDEV_95_PCT * (Xσ / Math.sqrt(n))) 

1.618208684980151

double


Where n is the number of samples and X is occupancy or delay.



Parameter

Explanation

Type

Example

Statistic_Name

Unique name for this block that will be printed in the BLOCK name field of the output data structure.

String

"Statistic_Name"

Sample_Every_Nth_DS

Sample every Nth data structure can be used for the purpose of computing the statistics, every value can be used (1) or every (Nth) value.

Integer

1

Batch_Count_Min_Max

Collect N batches (int), starting at Min time (double), end at Max time (double).   The number of batches can be 1.

List of 3 integers in a string or parameters

"1   0.0  TStop"



Port

Explanation

Type

stats_data

This is an input port for the data samples.

General

stats_trigger

This is an input port that triggers the current statistics to be placed on the output port.

General

stats_reset

This input port reset all internal statistics.

General

histo_output

The values can be plotted on a histogram Plotter block in VisualSim.

Double

output

Output the current Statistics when trigger on the stats_trigger port.

General



 

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