Re: [Boost-users] [random] Singleton engine

26 Jul 2009

      Thanks Robert,

Your singleton makes stuff really easy.

For those interested, code below works like a breeze. Destructor is
also called at program exit, so no leaks will occur.

Best,
Diederick
---
#pragma once

// includes
#include 
#include 
#include 
using namespace std;
namespace bs  = boost::serialization;

// declaration
template<class Dist>
class CRandom
{
public:
    /** use for Dist:
        CRandomI Ci(min,max);   uses uniform_int<int>       - integral types
        CRandomR Cr(min,max);   uses uniform_real<double>   - floating
point types

        for other ditributions or types, use:
        CRandom Cr(0--3 params, depending
on distribution);
        for distributions and params, see:
http://www.boost.org/doc/libs/1_39_0/libs/random/random-distributions.html

        engine is wrapped following singleton pattern, so every instantiation
        of CRandom uses the same engine. Singleton of boost::serialization used
    */

    // forwarding constructors
    explicit CRandom()
        : Gen(bs::singletonboost::mt19937::get_mutable_instance(), Dist())
    { }
    template<class P>
    explicit CRandom(const P & p1)
        : Gen(bs::singletonboost::mt19937::get_mutable_instance(), Dist(p1))
    { }
    template<class P>
    explicit CRandom(const P & p1, const P & p2)
        : Gen(bs::singletonboost::mt19937::get_mutable_instance(),
Dist(p1, p2))
    { }
    template<class P>
    explicit CRandom(const P & p1, const P & p2, const P & p3)
        : Gen(bs::singletonboost::mt19937::get_mutable_instance(),
Dist(p1, p2, p3))
    { }

    ~CRandom(void) {};

    typedef typename Dist::result_type result_type;

    result_type operator()() { return Gen(); }
    template<class T>
    result_type operator()(T value) { return Gen(value); }

private:
    boost::variate_generatorboost::mt19937&,Dist Gen;
};
// end declaration

// shorthand typedefs
typedef CRandom        CRandomI; // even int
is default type   , specify it in case it ever changes
typedef CRandom    CRandomR; // even
double is default type, specify it in case it ever changes

On Sun, Jul 26, 2009 at 1:54 PM, Diederick C.
Niehorster wrote:
...
Dear Robert,
Thanks! I will look into
http://www.boost.org/doc/libs/1_39_0/libs/serialization/doc/singleton.html,
I should not be reinventing the wheel ;)
Dear Steven,
Sharp eye, good point. Now two different numbers get generated and all
those destructor calls dissapeared.
It seems one too many dissapeared even (see program output below).
Even though MSVC does not complain about memory leaks, at end of
program the destructor never gets called. Lets see if Robert's
singleton class solves this, otherwise i suppose i should look into
using scoped_ptr?
Thanks a lot for your replies,
Diederick
------ output:
check 0
00000000
ctor 1
after ctor 1
003462E0
random: 8148
dtor 1
ctor 2
after ctor 2
003462E0
random: 1355
Press any key to continue . . .
On Sun, Jul 26, 2009 at 1:16 PM, Steven Watanabe wrote:
...
AMDG
Diederick C. Niehorster wrote:
...
template<class Dist>
class CRandom
{
public:
<snip>
private:
   boost::variate_generatorboost::mt19937,Dist Gen;
};
This copies the engine.  Try
boost::variate_generatorboost::mt19937&,Dist
In Christ,
Steven Watanabe
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