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

Za Ba Dar Yadegama , Nahid Sahar

""Za Ba Daryadegama"" is the 2nd poetry book of Miss. Nahid sahar. In this book she Published free verses poems and ghazals . . . Read More

Matter of Identity , Dr. Sher Zaman Taizai

The NWFP assembly at long last, passed the historic resolution on November 13, calling for naming this nameless province of Pakistan as Pakhtunkhwa. This day and event will be included as a golden chapter in the long and turbulent history of Pakhtuns, for which the provincial assembly deserves gratitude. The North West Frontier Province is not a name but identification of a geographical locality. . . . Read More

Dr. Sher Zaman Taizi; A Biography , Khurshid Iqbal Khattak

Hailing from the Taizi family of Momand tribe, Sher Zaman was born in 1931 in the house of Kator Shah at Pabbi. The matriculation certificate dated the first of November 1948 that he had received from the University of Punjab carries the date of his birth as 3 November 1931. . . . Read More

د اعتکاف احکام ، سعادت مشواڼي

معتکف ته دا اجازت نشته چې دجومات نه بهر ووځى البته دطبعى ضرورت لپاره وتلے شى يعنې دوړو او لويو بولو . . . نور

Flavours of Pashto Music , Dr. Raj Wali Shah Khattak


Pashtoon is a unique nation. The Pashtoons are a romantic people and extremely love music but don't like musicians. This seems very strange on their part . . . Read More


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

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)