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


A collection of Paintings compiled from various sources on the internet and books. . . . Read More

Badar Munir , Mudassar Shah


The life and Times of Bada Munir . . . Read More

Folklore of Afghanistan , Margaret A. Mills & Abdul Ali Ahrary

In Afghanistan in the 20th century, as in Persia until recently, a predominantly oral culture has long mingled with an established, elaborate literary tradition, both religious and secular, including prose and verse forms of verbal art. . . . Read More

ديو اهد شخص واقعه ، ترتيب: عارف بختيارپچيرے

دهارون الرشيد يو زوې ؤ چې دهغه عمر تقريباً شپاړس کاله ؤ هغه به ډير دزاهدانو او عارفانو په مجلس کښې ناست ؤ او زياتره به هديرې ته تلو هلته به ئې وئيل چې تاسو زمونږ نه مخکښې دنيا ته راغلى وے ددې دنيا تاسې ميلمانۀ وے خو تاسو ته دنيا خلاصون در نۀ کړو تر دې پورې چې قبرونو ته ورنه بې نوا لاړئ يوه ورځ دخپل پلار مجلس ته ورغے ددۀ پلار سره ټول وزيران او اميران . . . نور


The task expected of many English officers in the nineteenth century subcontinent appears overwhelming when viewed through the lens of today. It is quite extraordinary to conceive of how they would venture into lands rarely or never before seen by Western eyes, to speak to people who were accustomed to war and knew little of peace, alone but for a potentially hostile local army, . . . Read More


مدينه يونيورسټي سعدي عرب له خواه مقاله . . . نور

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;
}
}

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)