An M/M/n queuing model simulation with Object Pascal and my Thread Pool Engine - version 1.04
Author: Amine Moulay Ramdane
Email: aminer68@gmail.com
Description:
It's harder and sometimes impossible to get analytical results about waiting times and queue length for general interarrival and service distributions; so, it's important to be able to estimate these quantities by observing the results of simulation.
It's very easy in Object Pascal to simulate a sequence of arrival times with a given interarrival distribution.
Look at the examples MM1.pas( M/M/1 queuing model) and MMn.pas(M/M/n - n: number of servers -) inside the zip file:
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InterArrivals:=TExponentialDistribution.Create(420623,1.0/3.0);
ServiceTimes:=TExponentialDistribution.Create(220623,1.0/4.0);
currtime:=0.0;
for i:=1 to simnumber
do
begin
obj:=TJob.create;
obj.simnumber:=simnumber;
obj.number:=i;
currtime:=currtime+InterArrivals.Sample;
obj.ArrivalTime:=currtime;
obj.Servicetime:= ServiceTimes.sample;
TP.execute(myobj.myproc1,pointer(obj),NORMAL_PRIORITY);
end;
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Here we have the InterArrivals object and ServiceTimes object and we are calling InterArrivals.Sample to get our samples from the Exponential Distribution.
After that we are calling myobj.myproc1 to simulate our M/M/1 queuing model...
If you look at MMn.pas , you will see that the arrival rate is: 3 and the service rate is 4 , so, this will give us a theoretical value of 1/(4-3) = 1 for one server, and the Object Pascal simulation gave me 1.02 for one server.
You can go to download the zip files by clicking on the following web link:
https://drive.google.com/drive/folders/1-yB4E_9GdJDkVg0H6s6m1B_kZ5CBssW1?usp=sharing
Language: FPC Pascal v2.2.0+ / Delphi 7+:http://www.freepascal.org/
Operating Systems: Win , Linux and Mac (x86).
Required FPC switches: -O3 -Sd -dFPC -dWin32 -dFreePascal
-Sd for delphi mode....
Required Delphi switches: -DMSWINDOWS -$H+
For Delphi use -DDelphi
Required Delphi XE switches: -DMSWINDOWS -$H+ -DXE
The define options inside the defines.inc file:
{$DEFINE CPU32} for 32 bit systems
{$DEFINE CPU64} for 64 bit systems