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Old 12-18-2008, 04:15 AM   #1
shyan
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Registered: Dec 2008
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Red face What causes the segmentation fault during the course of simulation in ns-2.33?


This is the running procedure while I simulated using the a changed aodv protocol. I burrowed some portion of the code but I got the error of SEGMENTATION FAULT is there any way to track where is the error being generated from?

[Shyan@localhost bin]$ ./ns exp.tcl 10 1 traf scen 1 exp1.tr exp1.nam
num_nodes is set 10
warning: Please use -channel as shown in tcl/ex/wireless-mitf.tcl
Here Agent/AODV/MYAODV 1
INITIALIZE THE LIST xListHead
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Here Agent/AODV/MYAODV 1
Loading node movement...
Loading connection pattern...
Starting Simulation...
Here
Here
Here
Here
Here
Here
Here
Here
Here
channel.cc:sendUp - Calc highestAntennaZ_ and distCST_
highestAntennaZ_ = 1.5, distCST_ = 550.0
SORTING LISTS ...DONE!
Segmentation fault

How to get to this error?
 
Old 12-20-2008, 01:14 PM   #2
knudfl
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I'm no coder, so I can't help with straighten out errors
in that code. The text shown in # 1, won't give you any
answers.

But please read about "segmentation fault"
http://www.google.dk/search?hl=da&q=...meta=&aq=f&oq=

http://en.wikipedia.org/wiki/Segmentation_fault

If you do not find the failure in your code, please
show the code, and if you put it in "Code Tags" ,
you may even get an answer.
....
 
Old 12-20-2008, 01:38 PM   #3
business_kid
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Post

A segmentation fault is a memory error.

/begin history lesson
Back around the time of the 80286 design (when if you wanted windows you would have been referred to a carpenter) in the commercial "Our cpu has more <whatever> than yours" littleness that goes on, intel went to 20 address lines. But they only had 16 bit registers. This was sad and stupid. So they invented 4 bit paging or segmentation registers. Your ram addresses then had the paging register as the top 4 bits and the 16 other bits were the data register. Ram appeared on certain pages, not others (hence memory mapping, etc.)
/end history lesson

So when you address the ram on a page that doesn't exist, you got a segmentation fault. In fact, now it means a memory error. The program crashed, or your ram is buggy. Eliminate the letter with memtest86, and then email the maintainer.

I would grep exp.tcl for that word highestAntennaZ_ . From there it sorts things and crashes. Google has plenty on this:

http://www.google.ie/search?q=highes...ient=firefox-a

Seems like a known problem. You may have to go at it under instruction with gdb to sort yourself
 
  


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