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

To the Tribe on the Edge , Raza Khan Muhammadzai

There is very little authentic information available to the outside world about the Federally Administered Tribal Areas (FATA). The remoteness of the area, and the political vacuum . . . Read More

"Clasp the hands together ... this would be the North West Frontier", said my Pakistan studies teacher, referring to how Roos Keppel summarized the political and geographical situation of the province of his times. . . . Read More

د رمضان المبارک په بختوره مياشت کښې څوورځې وړاندې د هندکو شاعرانو اديبانو يوه ردنه نعيته مشاعره منعقدکړې وه چې مشرى ئې عبدالحليم صاحب ډاکټرظهور احمد اعوان او حاجى محمد عديل کوله. مشاعره کښې د صوبې ګڼ شمير کښې هند کى شاعرانو برخه . . . نور

عزيز الرحمن الفت پښتو ادب له پينځو ستوريو څخه د يوه ستوري استاز ګل پاچا الفت زوئ دې. په 1315 ل کال ئې د پروان ولايت د کوهستان په ولسوالي کښې دغې دنيا ته سترګې پرانيستې. د عزيز ارحمن پلونۍ کور د لغمان ولايت د قرغيو ولسوالي د کڅ په سيمه کښۍ دې. لومړنۍ او منځني زده کړې ئې د ننګرهار او حبيبي په ليسو کښۍ کړې دې. . . . نور

An account of the life of social worker and civil contractor Khan Mir Aslam Khan Khattak of Shaidu village, Nowshera. The write-up also presents a pictorial account of some step-based water-wells constructed by him. . . . Read More

په اسلامي کتابونو کې راغلي دي، چې پر ځمکه درې ډوله داسې مخلوقات دي، چې د يو او بل په ژوند کې مداخلې کوي، انسانان، پيريان او پلوشي . . . 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);
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)