Random Generation of bi-directional Graphs in Omnet :: Khyber.ORG

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Random Generation of bi-directional Graphs in Omnet, Omar Usman
Published in Khyber.ORG on Wednesday, July 4 2012 (http://www.khyber.org)


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The Omnet usman.html manual has code for generation of random topologies. The type of network generated can contain uni-directional, or bi-directional edges. Usually, people working with networks require generation of bi-directional graphs only. What you will see here is a small hack to the Omnet Engine, which can enable you to do that. . . . Read More

سيرت النبي صلي الله عليه وسلم په حواله ، علامه ابو الحسن علي ندوي

د سيرت په حواله د علامه ابو الحسن علي ندوي يو څو ليکنې د کتاب په شکل کښې ورکړ شوي دي. ژباړه کؤنکښې ډاکټر سعيد الله قاضي دې. . . . نور


Malakand agency lies at a strategically important position as it acts as a Gateway to Swat, Dir, Chitral and Bajaur. It is in the lower Swat region amidst high mountains thick with evergreen olive and pine trees. It stands at the exit of a pass known as Malakand Pass or Darrah Malakand; now much less difficult to cross than before as one travels from Peshawar to Swat. . . . Read More

چا ووژل ، افضل شوق

ملک غفور خان لور زرينه دخپل شوخ پيغلتوب او د زړۀ راښکونکى ښائست له وجې دکلى په ټولو پيغلو کښې ثانى نۀ لرله. څنګه چې په ښائست کښې دا يوه بريښنا وه، هم هغسې په طبيعت کښې بيخى زياته شوخه او مغرور فطرته جينۍ وه. دکلى دهر ځوان زړۀ به ارو مرو د زرينې سندرې وئيلې او هر کله به په دې کوشش کښې ؤ چې زرينه دې دهغه شى خو مجال نۀ ؤ چې زرينې ته به چا کاږۀ کتل . . . نور


ظلمونو غلتیانی نارواوی خو مو ډیری وکړی
کومه یوه به درته یادومه ستایم به یی
هم دا اوس تازه روانه پیښه چی ده
تا ولی د نیمروزقندوز په حملی ظلم باندی
څه ونه لیکل کوم فیغام د راونه لیږه؟؟ . . . نور

Kalash Calling , Nyla Daud

ONE of the major attractions of the Chitral valley is its fabled Kalash tribe. Traditionally called the wearers of black robes, they are a pagan tribe who some historians believe are descendants of five soldiers of the legions of Alexander's army. Today, just over 3,000 Kalash people live in the three valleys of Bumburiet, Birir and Rumbur. . . . Read More

Random Generation of bi-directional Graphs in Omnet

Omar Usman

Publishing Date: Wednesday, July 4 2012

The Omnet usman.html manual has code for generation of random topologies. The type of network generated can contain uni-directional, or bi-directional edges. Usually, people working with networks require generation of bi-directional graphs only. What you will see here is a small hack to the Omnet Engine, which can enable you to do that. (Note: I am not an expert on Omnet so most probably there is another simpler way of doing this. If you do, please leave a comment).

The files you need to modify are:

  1. src/sim/distrib.cc
  2. include/distrib.h
  3. src/sim/nedfunctions.cc

Modifications to distrib.cc

You need to create a new function (runiform). What this does is that it retains the random number generated from a previous call to uniform(). The random number is generated every 2-calls.

double runiform(int rng) {
static int r = 0;
static double l = 0;
if(r%2 == 0) l = uniform(0,1);
r++;
return l;
}

Modifications to distrib.h

Just one line to be modified here:

SIM_API double runiform(int rng=0);

Modifications to nedfunctions.cc

The current usman.html manual (July 4, 2012) shows a different way of doing this. The code in the manual is not consistent with what I found in the source (4.2.2). You need to add the following code to where the other continuous random variate generation code is present.

DEF(nedf_runiform,
"quantity runiform(int rng?)",
"random/continuous",
"Retains the value generated from a previous call to uniform()",
{
int rng = argc==2 ? (int)argv[1] : 0;
return cNEDValue(runiform(rng), argv[0].getUnit());
})

Compilation and Usage

If you have already compiled omnet once, you can simply run make and compile the engine again. When complete, fire up your editor and open your .NED file. You can now generate bi-directional graphs using the following code from the manual (which is adopted to this hack):

module RandomGraph {
parameters:
int count;
double connectedness; // 0.0 submodules:
node[count]: Node {
gates:
in[count];
out[count];
}
connections allowunconnected:
for i=0..count-1, for j=0..count-1 {
node[i].out[j] --> node[j].in[i]
if i<j && runiform() > connectedness;
node[j].out[i] --> node[i].in[j]
if i<j && runiform() > connectedness;
}
}

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Random Generation of bi-directional Graphs in Omnet, Omar Usman
Published in Khyber.ORG on Wednesday, July 4 2012 (http://www.khyber.org)