# Model for my problem (network simulator) **URL:** \ **Category:** ruby-talk\ **Created:** [3 May 2004 16:17 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338 "2004-05-03T16:17:14Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Gergely\_Kontra](https://avatars.discourse-cdn.com/v4/letter/g/7c8e57/32.png) [@Gergely\_Kontra](https://rubytalk.org/u/Gergely_Kontra)\ **Post date:** [3 May 2004 16:17 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/1 "2004-05-03T16:17:14Z")
Hello! I’d like to ask for help for my problem. Maybe the Q isn’t ruby-specific, but I WILL implement it in ruby, and I want to make a rubyish program. I hope I can learn from the problem. So: I had to write a network simulator. It consists of nodes, link between nodes. The delay of the link should be user-programmable (maybe proc is the right way, but it must be evaluated in the object’s scope, because delay is not independent of the link’s state… And finally the simulator has agents. Agents are programs, which can migrate. Migration is requested by agent. (Request goes to the node, and the node does the actual migration…) Agent must know about their own location, it can ask the node about outgoing links (so nodes must know about links ending at the node, of course). Shall I submit my code? Or did anybody has a model for it already? thx in advance Gergo > **···** > > – > ±[Kontra, Gergely[kgergely@mcl.hu](mailto:kgergely@mcl.hu) PhD student Room IB113 ]---------+ > > > [http://www.mcl.hu/~kgergely](http://www.mcl.hu/~kgergely) “Olyan langesz vagyok, hogy | > > Mobil:(+36 20) 356 9656 ICQ: 175564914 poroltoval kellene jarnom” | > > ±- Magyar php mirror es magyar php dokumentacio: [http://hu.php.net](http://hu.php.net) --+ ---
**Author:** ![Robert](https://avatars.discourse-cdn.com/v4/letter/r/e95f7d/32.png) [@Robert](https://rubytalk.org/u/Robert)\ **Post date:** [3 May 2004 16:59 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/2 "2004-05-03T16:59:00Z")
“Gergely Kontra” [kgergely@mcl.hu](mailto:kgergely@mcl.hu) schrieb im Newsbeitrag news:20040503161710.GA16300@mlabdial.hit.bme.hu… > Hello! > > I’d like to ask for help for my problem. Maybe the Q isn’t > ruby-specific, but I WILL implement it in ruby, and I want to make a > rubyish program. I hope I can learn from the problem. > > So: I had to write a network simulator. It consists of nodes, link > between nodes. The delay of the link should be user-programmable (maybe > proc is the right way, but it must be evaluated in the object’s scope, > because delay is not independent of the link’s state… > > And finally the simulator has agents. Agents are programs, which can > migrate. Migration is requested by agent. (Request goes to the node, and > the node does the actual migration…) > Agent must know about their own location, it can ask the node about > outgoing links (so nodes must know about links ending at the node, of > course). > > Shall I submit my code? Or did anybody has a model for it already? What was your question exactly? You seem to have implemented the simulator already… As a general OO rule of thumb, take all the interesting nouns and make them classes. This seems to be pretty much straightforward in your case. The thing I find more interesting is the scheduling. This could be done like this (attached). Regards ``` robert ``` [schedule.rb](https://rubytalk.org/uploads/short-url/5T8DWLnODvlqp1vrAp7TSOsnoms.rb) (1021 Bytes) ---
**Author:** ![Gergely\_Kontra](https://avatars.discourse-cdn.com/v4/letter/g/7c8e57/32.png) [@Gergely\_Kontra](https://rubytalk.org/u/Gergely_Kontra)\ **Post date:** [4 May 2004 12:13 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/3 "2004-05-04T12:13:23Z")
Hey! I have almost the same code for scheduling. I just used something similar to this. The only difference: I used relative time, so my method is called after… Maybe it worth to make something generally usable? BTW Hash.new {|h,k| h[k]= } can be written as Hash.new {} > **···** > > On 0504, Robert Klemme wrote: > > > The thing I find more interesting is the scheduling. This could be done > > like this (attached). > > – > > ±[Kontra, Gergely[kgergely@mcl.hu](mailto:kgergely@mcl.hu) PhD student Room IB113 ]---------+ > > [http://www.mcl.hu/~kgergely](http://www.mcl.hu/~kgergely) “Olyan langesz vagyok, hogy | > > Mobil:(+36 20) 356 9656 ICQ: 175564914 poroltoval kellene jarnom” | > > ±- Magyar php mirror es magyar php dokumentacio: [http://hu.php.net](http://hu.php.net) --+ ---
**Author:** ![Gergely\_Kontra](https://avatars.discourse-cdn.com/v4/letter/g/7c8e57/32.png) [@Gergely\_Kontra](https://rubytalk.org/u/Gergely_Kontra)\ **Post date:** [6 May 2004 13:05 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/4 "2004-05-06T13:05:29Z")
Just one little thing (chicken-egg problem): the links should know about the 2 ending nodes, and nodes must know about in/outgoing links. So how to easily administrate it? Gergo > **···** > > On 0504, Robert Klemme wrote: > > > > I’d like to ask for help for my problem. Maybe the Q isn’t > > > ruby-specific, but I WILL implement it in ruby, and I want to make a > > > rubyish program. I hope I can learn from the problem. > > > > > > So: I had to write a network simulator. It consists of nodes, link > > > between nodes. The delay of the link should be user-programmable (maybe > > > proc is the right way, but it must be evaluated in the object’s scope, > > > because delay is not independent of the link’s state… > > > > > > And finally the simulator has agents. Agents are programs, which can > > > migrate. Migration is requested by agent. (Request goes to the node, and > > > the node does the actual migration…) > > > Agent must know about their own location, it can ask the node about > > > outgoing links (so nodes must know about links ending at the node, of > > > course). > > > > > > Shall I submit my code? Or did anybody has a model for it already? > > > > What was your question exactly? You seem to have implemented the simulator > > already… > > – > ±[Kontra, Gergely[kgergely@mcl.hu](mailto:kgergely@mcl.hu) PhD student Room IB113 ]---------+ > > > [http://www.mcl.hu/~kgergely](http://www.mcl.hu/~kgergely) “Olyan langesz vagyok, hogy | > > Mobil:(+36 20) 356 9656 ICQ: 175564914 poroltoval kellene jarnom” | > > ±- Magyar php mirror es magyar php dokumentacio: [http://hu.php.net](http://hu.php.net) --+ ---
**Author:** ![Robert](https://avatars.discourse-cdn.com/v4/letter/r/e95f7d/32.png) [@Robert](https://rubytalk.org/u/Robert)\ **Post date:** [4 May 2004 12:49 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/5 "2004-05-04T12:49:02Z")
“Gergely Kontra” [kgergely@mcl.hu](mailto:kgergely@mcl.hu) schrieb im Newsbeitrag news:20040504121319.GA27180@mlabdial.hit.bme.hu… > > The thing I find more interesting is the scheduling. This could be > > done > > like this (attached). > > Hey! > > I have almost the same code for scheduling. I just used something > > similar to this. The only difference: I used relative time, so my method > > is called after… Do you convert to abs time internally or how do you make sure the order is correct? > Maybe it worth to make something generally usable? =\> RAA > BTW > Hash.new {|h,k| h[k]= } can be written as > Hash.new {} Nope, that’s not the same: irb(main):001:0\> h=Hash.new {} =\> {} irb(main):002:0\> h[1] =\> irb(main):003:0\> h =\> {} irb(main):004:0\> h=Hash.new {|h,k| h[k]=} =\> {} irb(main):005:0\> h[1] =\> irb(main):006:0\> h =\> {1=\>} irb(main):007:0\> RUBY\_VERSION =\> “1.8.1” Your solution makes the idiom “h[key] \<\< something” unusable since all those arrays never make it into the hash. ``` robert ``` > **···** > > > On 0504, Robert Klemme wrote: ---
**Author:** ![Zsban\_Ambrus](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@Zsban\_Ambrus](https://rubytalk.org/u/Zsban_Ambrus)\ **Post date:** [6 May 2004 13:26 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/6 "2004-05-06T13:26:54Z")
> > > I’d like to ask for help for my problem. Maybe the Q isn’t > > > ruby-specific, but I WILL implement it in ruby, and I want to make a > > > rubyish program. I hope I can learn from the problem. “rubyish program” – does this mean a program in ruby? probably since you post this here > > > So: I had to write a network simulator. It consists of nodes, link > > > between nodes. > > > … > > > > > > Shall I submit my code? Or did anybody has a model for it already? > > > > What was your question exactly? You seem to have implemented the simulator > > already… > > Just one little thing (chicken-egg problem): the links should know about > the 2 ending nodes, and nodes must know about in/outgoing links. So how > to easily administrate it? That’s easy in ruby, as ruby is garbage-collected, so it can clean up circular references by itself. Thus, you can add a list of both the in and outgoing links to each nodes. > **···** > > On Thu, May 06, 2004 at 10:05:29PM +0900, Gergely Kontra wrote: > > > On 0504, Robert Klemme wrote: ---
**Author:** ![Gergely\_Kontra](https://avatars.discourse-cdn.com/v4/letter/g/7c8e57/32.png) [@Gergely\_Kontra](https://rubytalk.org/u/Gergely_Kontra)\ **Post date:** [4 May 2004 12:55 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/7 "2004-05-04T12:55:36Z")
Oh, yes, I run into the problem, and this is the weird case, where h[key] \<\< something and h[key] \<\<= something is different… Gergo > **···** > > On 0504, Robert Klemme wrote: > > > Nope, that’s not the same: > > irb(main):001:0\> h=Hash.new {} > > irb(main):002:0\> h[1] > > irb(main):003:0\> h > > =\> {} > > irb(main):004:0\> h=Hash.new {|h,k| h[k]=} > > irb(main):005:0\> h[1] > > irb(main):006:0\> h > > =\> {1=\>} > > Your solution makes the idiom “h[key] \<\< something” unusable since all > > those arrays never make it into the hash. > > – > ±[Kontra, Gergely[kgergely@mcl.hu](mailto:kgergely@mcl.hu) PhD student Room IB113 ]---------+ > > > [http://www.mcl.hu/~kgergely](http://www.mcl.hu/~kgergely) “Olyan langesz vagyok, hogy | > > Mobil:(+36 20) 356 9656 ICQ: 175564914 poroltoval kellene jarnom” | > > ±- Magyar php mirror es magyar php dokumentacio: [http://hu.php.net](http://hu.php.net) --+ ---
**Author:** ![Robert](https://avatars.discourse-cdn.com/v4/letter/r/e95f7d/32.png) [@Robert](https://rubytalk.org/u/Robert)\ **Post date:** [6 May 2004 15:18 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/8 "2004-05-06T15:18:58Z")
“Zsban Ambrus” [ambrus@math.bme.hu](mailto:ambrus@math.bme.hu) schrieb im Newsbeitrag news:20040506132651.GB3743@math.bme.hu… > > > > I’d like to ask for help for my problem. Maybe the Q isn’t > > > > ruby-specific, but I WILL implement it in ruby, and I want to make > > > > a > > > > rubyish program. I hope I can learn from the problem. > > “rubyish program” – does this mean a program in ruby? probably since > you post this here > > > > > So: I had to write a network simulator. It consists of nodes, link > > > > between nodes. > > > > … > > > > > > > > Shall I submit my code? Or did anybody has a model for it already? > > > > > > What was your question exactly? You seem to have implemented the > > > simulator > > > already… > > > > Just one little thing (chicken-egg problem): the links should know > > about > > the 2 ending nodes, and nodes must know about in/outgoing links. So > > how > > to easily administrate it? > > That’s easy in ruby, as ruby is garbage-collected, so it can clean up > circular references by itself. Thus, you can add a list of both the in > and > outgoing links to each nodes. IMHO the question was rather how to manage those references so that they are always in sync. That would be the typical problem with bi directional references in OO languages. Typically you manually have to write code for that (unless you find a library that does it gracefully) but if done properly you need to do it only once and can then reuse that code. ``` robert ``` > **···** > > > On Thu, May 06, 2004 at 10:05:29PM +0900, Gergely Kontra wrote: > > > > > On 0504, Robert Klemme wrote: ---
**Author:** ![Robert](https://avatars.discourse-cdn.com/v4/letter/r/e95f7d/32.png) [@Robert](https://rubytalk.org/u/Robert)\ **Post date:** [4 May 2004 16:48 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/9 "2004-05-04T16:48:56Z")
“Gergely Kontra” [kgergely@mcl.hu](mailto:kgergely@mcl.hu) schrieb im Newsbeitrag news:20040504125533.GB27180@mlabdial.hit.bme.hu… > **···** > > > On 0504, Robert Klemme wrote: > > > > > Nope, that’s not the same: > > > irb(main):001:0\> h=Hash.new {} > > > irb(main):002:0\> h[1] > > > irb(main):003:0\> h > > > =\> {} > > > irb(main):004:0\> h=Hash.new {|h,k| h[k]=} > > > irb(main):005:0\> h[1] > > > irb(main):006:0\> h > > > =\> {1=\>} > > > Your solution makes the idiom “h[key] \<\< something” unusable since all > > > those arrays never make it into the hash. > > > > Oh, yes, I run into the problem, and this is the weird case, where > > h[key] \<\< something and h[key] \<\<= something is different… > > Note also that h[key] \<\< something is more efficient since it does only one > hash lookup and no hash update. > > Regards > > ``` > robert > > ``` ---
**Author:** ![Claus\_Spitzer](https://avatars.discourse-cdn.com/v4/letter/c/49beb7/32.png) [@Claus\_Spitzer](https://rubytalk.org/u/Claus_Spitzer)\ **Post date:** [6 May 2004 16:43 UTC](https://rubytalk.org/t/model-for-my-problem-network-simulator/11338/10 "2004-05-06T16:43:15Z")
8\< snip > > > Just one little thing (chicken-egg problem): the links should know > > > about > > > the 2 ending nodes, and nodes must know about in/outgoing links. So > > > how > > > to easily administrate it? > > > > That’s easy in ruby, as ruby is garbage-collected, so it can clean up > > circular references by itself. Thus, you can add a list of both the in > > and > > outgoing links to each nodes. > > IMHO the question was rather how to manage those references so that they > are always in sync. That would be the typical problem with bi directional > references in OO languages. Typically you manually have to write code for > that (unless you find a library that does it gracefully) but if done > properly you need to do it only once and can then reuse that code. > > ``` > robert > > ``` Probably (and that is _only_ probably, as in “this is how I have seen it implemented in other instances by very smart professors”) you’ll want do do something along the lines of: - both the nodes and links have a list of what is attached to them. - both are observers and observables - a change in the node notifies the link, and vice-versa Otherwise, if for example only the links initiates the change, then you can make them be the observables and the nodes just the observers. Cheers! -CWS