Re: nsclick rng support for ns3

Hi Eddie,

but shouldn't we allow seeding the userlevel random number generator, in
case there is no support for ns3 random numbers?

I do not have any git repositories and do not understand git workflows
very well. Do i have to create a github repository as a fork of the
click git repository to issue pull requests? Or does any other git
repository work, too?

Sascha

On 25.01.2013 15:34, Eddie Kohler wrote:
> Hi Sascha!
> 
> I like this one much better, and checked in a version of it with a few changes.
> - Explicit case for srandom() which does nothing
> - Don't chatter if no node, just fall back to user level
> - No userlevel_random(), just put click_random() in ns/nsclick.cc
> 
> I hope it works for you. If it doesn't, send a pull request?
> E
> 
> On Fri, Jan 25, 2013 at 7:06 AM, Sascha Alexander Jopen
> <[email protected]> wrote:
>> Hey,
>>
>> i just tested this new patchset for random number support. It includes
>> fallback to userlevel random() or rand() in case of lacking support on
>> the ns3 side. Furthermore, ns3 returns random numbers in the range [0,
>> CLICK_RAND_MAX] whatever CLICK_RAND_MAX is on the platform where click
>> was compiled, as long as CLICK_RAND_MAX <= 0xFFFFFFFFU. This is done by
>> sending the actual CLICK_RAND_MAX value along with simclick_sim_command.
>> The ns3 side patch includes the changes suggested by Lalith.
>> Is this an acceptable solution?
>>
>> Regards,
>> Sascha
>>
>> On 23.01.2013 18:54, Eddie Kohler wrote:
>>> Why not just set the CLICK_RAND_MAX to 0x7FFFFFFFU, which NS can handle
>>> as well as normal code?
>>>
>>> Eddie
>>>
>>>
>>> On 1/23/13 12:35 PM, Sascha Alexander Jopen wrote:
>>>> Hi Eddie,
>>>>
>>>> I did not implement a fallback method, because i was not sure how to
>>>> handle CLICK_RAND_MAX in case a fall back is necessary. In
>>>> include/click/glue.hh CLICK_RAND_MAX is defined as the maximum value
>>>> supported by the ns3 implementation. However, if we find the simulator
>>>> not supporting random numbers at runtime, falling back to random() or
>>>> rand() could lead to a RAND_MAX, which is different from the defined
>>>> CLICK_RAND_MAX. This could lead to unexpected simulation behaviour. Any
>>>> comments, how to handle this?
>>>>
>>>> Regarding the CLICK_RAND_MAX value itself, i can change the maximum
>>>> value to 0xFFFFFFFFU.
>>>>
>>>> I used 0xFFFFFFFEU in the first place, because, although the ns3
>>>> documentation says, that calling
>>>>
>>>>    uint32_t GetInteger(uint32_t min, uint32_t max)
>>>>
>>>> returns an integer in the range [min,max], this seems not to be true for
>>>> max = 0xFFFFFFFFU. Because this calls internally another method, with
>>>> GetValue(min, max + 1), this results in an overflow. So 0xFFFFFFFEU
>>>> would be the largest possible integer. See around line 187 in file
>>>> src/core/model/random-variable-stream.cc. Either i'm wrong, or this is
>>>> something to report to the ns3 team.
>>>>
>>>> However, i certainly missed the alternative call with a cast of the max
>>>> value 0xFFFFFFFFU to double and back to uint32_t after a call to the
>>>> double based GetValue function. This would lead to a RAND_MAX of
>>>> 0xFFFFFFFFU. I will fix this.
>>>>
>>>> Thanks for reviewing,
>>>> Sascha
>>>>
>>>> On 23.01.2013 16:52, Eddie Kohler wrote:
>>>>> Hey,
>>>>>
>>>>> Two comments.
>>>>> - Breaking random numbers except for nses that export random numbers
>>>>> considered lame. Why not fall back to the normal random number
>>>>> generator?
>>>>> - The RAND_MAX value seems odd. (-2??) Why this value?
>>>>>
>>>>> Eddie
>>>>>
>>>>> On Wed, Jan 23, 2013 at 3:52 AM, Lalith Suresh
>>>>> <[email protected]> wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On Mon, Jan 21, 2013 at 12:16 PM, Sascha Alexander Jopen
>>>>>> <[email protected]> wrote:
>>>>>>> Hey,
>>>>>>>
>>>>>>> please find attached a patchset for click and ns3 which adds
>>>>>>> support for
>>>>>>> drawing random numbers within click simulations from the underlying
>>>>>>> ns3
>>>>>>> random number generator. Each simulated click node has its own
>>>>>>> uniformly
>>>>>>> distributed random number stream (as opposed to my previously
>>>>>>> submitted
>>>>>>> patch). This way all nodes have independent random number streams.
>>>>>>>
>>>>>>> Setting the seed or run numbers is done within the simulation by
>>>>>>> means of
>>>>>>>
>>>>>>> RngSeedManager::SetSeed ();
>>>>>>> RngSeedManager::SetRun ();
>>>>>>>
>>>>>>> or with environment variables or command line parameters.
>>>>>>> See http://www.nsnam.org/docs/manual/html/random-variables.html
>>>>>>>
>>>>>>> I still have no ns2 available. Currently, missing rng support from the
>>>>>>> simulator side is detected and reported but no random numbers are
>>>>>>> available to the simulation. Implementing a fallback method should be
>>>>>>> possible, however. Maybe someone who uses ns2 could provide this?
>>>>>>>
>>>>>>> click-ns3-rng.diff is for the click side and ns3-nsclick-rng.diff for
>>>>>>> the ns3 side.
>>>>>>>
>>>>>>
>>>>>> I had a look through this patch. For clarity, my comment is to rename
>>>>>> the simclick command to SIMCLICK_GET_RANDOM_INT and the
>>>>>> Ipv4ClickRouting method's name to GetRandomVariable(). Otherwise, it
>>>>>> looks good.
>>>>>>
>>>>>> I can push this to ns-3-dev when the click side gets committed.
>>>>>>
>>>>>>> Regards,
>>>>>>> Sascha
>>>>>>>
>>>>>>> --
>>>>>>> Dipl.-Inform. Sascha Jopen
>>>>>>>
>>>>>>> University of Bonn                     Tel.:   +49-228-73-54219
>>>>>>> Institute of Computer Science 4        Fax:    +49-228-73-4571
>>>>>>> Friedrich-Ebert-Allee 144              E-mail: [email protected]
>>>>>>> D-53113 Bonn, Germany
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> click mailing list
>>>>>>> [email protected]
>>>>>>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Lalith Suresh
>>>>>> www.lalith.in
>>>>>> _______________________________________________
>>>>>> click mailing list
>>>>>> [email protected]
>>>>>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>>>>
>>>>
>>
>>
>> --
>> Dipl.-Inform. Sascha Jopen
>>
>> University of Bonn                     Tel.:   +49-228-73-54219
>> Institute of Computer Science 4        Fax:    +49-228-73-4571
>> Friedrich-Ebert-Allee 144              E-mail: [email protected]
>> D-53113 Bonn, Germany


-- 
Dipl.-Inform. Sascha Jopen

University of Bonn                     Tel.:   +49-228-73-54219
Institute of Computer Science 4        Fax:    +49-228-73-4571
Friedrich-Ebert-Allee 144              E-mail: [email protected]
D-53113 Bonn, Germany