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

پښتو :: پښتانه :: پښتونخواه :: پښتونوالی

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

New Additions

[an error occurred while processing this directive]

From Archives

Which place in Pakistan do you think is the most beautiful? I am asked whenever I return from one of my travels into the remote hinter-lands of Pakistan. I really can't say for sure . . . Read More

It is said that all the credit of the beautification of the Hujrah goes to the Chillum, i.e., without it the Hujrah will be incomplete and dull. Men get together for their evening discussions, prepare a chillum or two, and pass it around as the night lingers on. . . . Read More

Tazkira Awlia , Suleiman Mako

Tazkerat Al Awlia is the oldest work of prose in Pashto that we know of. It was written in 612 Hijri (1216 AD) by Suleiman Mako (of Arghasan). Only 7 pages of the book were found by Prof. Abdul Hai Habibi. . . . Read More

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

Syed Muhammad Hubaan , Muhammad Shafi Sabir

The Tehreek e Mujahideen is rightly considered a very important, popular, and successful movement. A well renowned historian of modern times, Toin B. states that the Tehreek e Mujahideen was the first such movement meant for freeing the Muslims of the sub continent from the hands of the British and their cronies; the Sikhs and Hindus. . . . Read More

At the dawn of seventeenth century, at the age of invasions from the West by Persians and East by Moghols, a the time when Afghans were in the mist of war in every corner of the nation, a the time when education was the last thing in peoples' mind, a legend was born. . . . 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);
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.

"quantity runiform(int rng?)",
"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 {
int count;
double connectedness; // 0.0 submodules:
node[count]: Node {
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;

Comments powered by Disqus

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