Re: [Boost-users] seeding a boost::random number generator...?

From: Mikko Vainio (mivainio_at_[hidden])
Date: 2007-10-24 02:08:51

mersenneTwister.seed( static_cast<boost::mt19937::result_type>(s) );

Avoiding hard-coded types is always a good idea.

/Mikko

Graham Reitz wrote:
> Ok I got it.  Yikes, talk about type safety.   It really, really,
> wanted a boost::uint32_t for the seed parameter.
> 
> I passed it a double to see what kind of warning I would receive,
> hoping it would tell me what the parent time is:
> 
> warning: passing `double' for converting 1 of `void
> boost::random::mersenne_twister<UIntType, w, n, m, r, a, u, s, b, t
> , c, l, val>::seed(UIntType) [with UIntType = boost::uint32_t, int w =
> 32, int n = 624, int m = 397, int r = 31, UIntType a = -1727483681u,
> int u = 11, int s = 7, UIntType b = -1658038656u, int t = 15
> , UIntType c = -272236544u, int l = 18, UIntType val = -948541730u]'
> 
> Thanks again,
> Graham
> 
> On 10/23/07, Graham Reitz <graham.cpp_at_[hidden]> wrote:
>> Thanks for the reply Mike.   I am still stumped.  Any ideas on how I
>> can tell what type the "DataType" is?
>>
>> Graham
>>
>> On 10/23/07, Michael Linck <mgl_at_[hidden]> wrote:
>>> Looks like you seed it by converting your time stamp to whatever
>>> "DataType" you're trying to get back and using it as an arg to seed:
>>> "
>>> lass random::mersenne_twister
>>> {
>>> public:
>>>   typedef DataType result_type;
>>>   .
>>> .
>>> .
>>>   void seed();
>>>   void seed(DataType value);
>>>  " -- http://www.boost.org/libs/random/random-generators.html#mersenne_twister
>>>
>>> Or you can take the - possibly more complicated - route of trying to figure out how to use the Generator template.
>>>
>>> Hope that helps,
>>>
>>> mike
>>>
>>> On Tue, 2007-10-23 at 12:00 -0500, Graham Reitz wrote:
>>>> I am little confused on how to see a random generator.
>>>>
>>>> What am I missing?
>>>>
>>>>     // Grab the seed
>>>>     HighResTimer::Time time_secs = high_res_timer.getTime();
>>>>
>>>>     // Go ahead and truncate, it's just a seed
>>>>     boost::int32_t time = static_cast<boost::int32_t>(time_secs * 100000);
>>>>
>>>>     // produces randomness out of thin air
>>>>     // see pseudo-random number generators
>>>>     boost::mt19937 rng;
>>>>     rng.seed();  // How do you seed this with the time?
>>>>
>>>>     // distribution that maps to 0..1
>>>>     // see random number distributions
>>>>     boost::uniform_real<> zero_to_one(0,1);
>>>>
>>>>     // glues randomness with mapping
>>>>     boost::variate_generator<boost::mt19937&, boost::uniform_real<> >
>>>>         be_random zero_to_one);
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-- 
:: Mikko Vainio <mikko.vainio_at_[hidden]> tel + 358 2 215 4600
:: Structural Bioinformatics Laboratory
:: Department of Biochemistry and Pharmacy
:: Abo Akademi University, Tykistokatu 6A, FI-20520 Turku Finland