Lifetime of dynamically allocated boost:vector<> ?

Bobu (7)
Hi,

Currently I am working on a little project, where I'm facing a problem concerning the lifetime of dynamically allocated boost-vectors. At least I think this is where the problem lies.

I've broken down my code to a minimum, to show you, what the problem is about.

So, what should my code do?
I made a class, which holds two functions, the constructor and a pointer to a multi-dimensional array.
Within the constructor, the multi-dim array is created. 
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typedef boost::multi_array<p_vec, 2> array_type2d;
typedef array_type2d::index index2;

The elements of the multi-dim array are pointers to boost::numeric::ublas::vector<double> (called p_vec).
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using namespace boost::numeric::ublas;
typedef vector<double>* p_vec;

This works, but when i want to access this vector from a second function i get 

[1](0)
[1](1)
[1](2)
[1](1)
[1](2)
[1](3)
[1](2)
[1](3)
[1](4)
sandbox: /usr/include/boost/multi_array/base.hpp:177: Reference boost::detail::m
ulti_array::value_accessor_one<T>::access(boost::type<Reference>, boost::multi_a
rray_types::index, TPtr, const boost::multi_array_types::size_type*, const boost
::multi_array_types::index*, const boost::multi_array_types::index*) const [with
 Reference = boost::numeric::ublas::vector<double, boost::numeric::ublas::unboun
ded_array<double, std::allocator<double> > >*&, TPtr = boost::numeric::ublas::ve
ctor<double, boost::numeric::ublas::unbounded_array<double, std::allocator<doubl
e> > >**, T = boost::numeric::ublas::vector<double, boost::numeric::ublas::unbou
nded_array<double, std::allocator<double> > >*]: Assertion `idx - index_bases[0]
 >= 0' failed.


The first part of the output simply shows the dynamically created vector<double> (first integer represents the size of the vector, which is one, and the second double is the value, which is stored).

This is my code:

main.cpp:

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#include "test_cpu1_2.hpp"
int main(){
	cell_method cell1;
	cell1.interactions();

	return 0;
}


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#include <boost/numeric/ublas/vector.hpp>
#include <boost/numeric/ublas/io.hpp>
#include <boost/multi_array.hpp>
#include <stdio.h>

using namespace boost::numeric::ublas;
typedef vector<double>* p_vec;

typedef boost::multi_array<p_vec, 2> array_type2d;
typedef array_type2d::index index2;

class cell_method
{
public:
	cell_method(void);
	void create_cells(void);
	void interactions();

	array_type2d* pcell_2d;
};

cell_method::cell_method(){
	array_type2d cell_2d(boost::extents[3][3]);
	pcell_2d = &cell_2d;

	create_cells();
};

void cell_method::create_cells(){
	for(int i = 0; i < 3;++i){
		for(int j = 0; j < 3; ++j){
			p_vec p_vec2 = new vector<double>;
			(*pcell_2d)[i][j] = p_vec2;
			(*(*pcell_2d)[i][j]).resize(1);
			(*(*pcell_2d)[i][j])(0) = i + j;
			std::cout << (*(*pcell_2d)[i][j]) << std::endl;
		}
	}
};

void cell_method::interactions(){
	std::cout << (*(*pcell_2d)[1][1]) << std::endl;
}


regards,
juergen
Last edited on
rollie (304)
I was reading up on all the boost functionality for a while to answer this, and couldn't figure out why the code wasn't working. Then I saw 

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array_type2d cell_2d(boost::extents[3][3]);
pcell_2d = &cell_2d;


you are setting your pcell_2d data member to a local variable in the cell_method constructor. When that function returns, the local variable goes away, and your pcell_2d member is not pointing to bad data. You can make pcell_2d a non-ptr, or allocate it with 'new'.
Bobu (7)
Thx very, very much!!!
I've tried every possibility to make this little code working, but i didn't thought, that at this code line was the problem :)

pcell_2d = new array_type2d(boost::extents[3][3]);
works just perfect!!

Best wishes,
juergen
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