[Boost-users] Boost.Random mt19937 seeding

From: Matt Holland (mdholland_at_[hidden])
Date: 2006-08-09 21:26:22

Hi all,

I'm having some difficulty understanding my options for seeding the 
base generators in mersenne_twister.hpp.  I'm interested in the array 
initialization that is somewhat obtusely mentioned in the 
documentation.  In boost/random/mersenne_twister.hpp I see the 
following relevant items:

template<class It> mersenne_twister(It& first, It last) { 
seed(first,last); }

...

template<class It>
void seed(It& first, It last)
{
        int j;
        for(j = 0; j < n && first != last; ++j, ++first)
                x[j] = *first;
        i = n;
        if(first == last && j < n)
                throw std::invalid_argument("mersenne_twister::seed");
}

I gather that "It" is some kind of iterator, and the natural candidate 
would be something like std::vector<uint32_t>::iterator, but not having 
truly come to terms with templates, it is unclear to me how to actually 
call this.  The following minimal code snippet fails to compile with 
g++ (gcc version 3.3 20030304 (Apple Computer, Inc. build 1671)).  
Errors below.

#include <iostream>
#include <vector>
#include <boost/random.hpp>

typedef boost::mt19937 Mt19937BaseGenerator; // base generator
typedef boost::uniform_real<> UniformReal; // distribution
// variate generator
typedef boost::variate_generator<Mt19937BaseGenerator&, UniformReal> 
Mt19937UniformRealGenerator;

int main() {
   std::vector<uint32_t> seedVector(4);
   seedVector[0] = 12345u; // make up some seeds
   seedVector[1] = 98765u;
   seedVector[2] = 12942u;
   seedVector[3] = 20343u;

   // attempt to seed with vector iterators
   Mt19937BaseGenerator mt19937Generator(seedVector.begin(), 
seedVector.end());
   UniformReal distribution(0, 1);
   Mt19937UniformRealGenerator myGen(mt19937Generator, distribution);

   for (unsigned i = 0; i < 100; ++i) {
     std::cout << myGen() << std::endl;
   }

   return 0;
}

mt19937Seed.cpp: In function `int main()':
mt19937Seed.cpp:18: error: no matching function for call to `
    boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 
0x09908b0df, 11,
    7, 0x09d2c5680, 15, 0x0efc60000, 18, 0x0c77666de>::mersenne_twister(
    __gnu_cxx::__normal_iterator<uint32_t*, std::vector<uint32_t,
    std::allocator<uint32_t> > >, __gnu_cxx::__normal_iterator<uint32_t*,
    std::vector<uint32_t, std::allocator<uint32_t> > >)'
/sw/include/boost/random/mersenne_twister.hpp:43: error: candidates are:
    boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 
0x09908b0df, 11,
    7, 0x09d2c5680, 15, 0x0efc60000, 18, 
0x0c77666de>::mersenne_twister(const
    boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 
0x09908b0df, 11,
    7, 0x09d2c5680, 15, 0x0efc60000, 18, 0x0c77666de>&)
/sw/include/boost/random/mersenne_twister.hpp:69: error:
    boost::random::mersenne_twister<UIntType, w, n, m, r, a, u, s, b, t, 
c, l,
    val>::mersenne_twister(It&, It) [with It =
    __gnu_cxx::__normal_iterator<uint32_t*, std::vector<uint32_t,
    std::allocator<uint32_t> > >, UIntType = uint32_t, int w = 32, int n 
= 624,
    int m = 397, int r = 31, UIntType a = 0x09908b0df, int u = 11, int s 
= 7,
    UIntType b = 0x09d2c5680, int t = 15, UIntType c = 0x0efc60000, int 
l = 18,
    UIntType val = 0x0c77666de]
/sw/include/boost/random/mersenne_twister.hpp:68: error:
    boost::random::mersenne_twister<UIntType, w, n, m, r, a, u, s, b, t, 
c, l,
    val>::mersenne_twister(UIntType) [with UIntType = uint32_t, int w = 
32, int
    n = 624, int m = 397, int r = 31, UIntType a = 0x09908b0df, int u = 
11, int
    s = 7, UIntType b = 0x09d2c5680, int t = 15, UIntType c = 
0x0efc60000, int l
    = 18, UIntType val = 0x0c77666de]
/sw/include/boost/random/mersenne_twister.hpp:60: error:
    boost::random::mersenne_twister<UIntType, w, n, m, r, a, u, s, b, t, 
c, l,
    val>::mersenne_twister() [with UIntType = uint32_t, int w = 32, int 
n = 624,
    int m = 397, int r = 31, UIntType a = 0x09908b0df, int u = 11, int s 
= 7,
    UIntType b = 0x09d2c5680, int t = 15, UIntType c = 0x0efc60000, int 
l = 18,
    UIntType val = 0x0c77666de]

Any help?  I always have a really hard time interpreting 
template-related compiler errors.

Thanks,
Matt

--
Matt Holland
Population Biology Graduate Group
University of California
Davis, CA 95616