Memory Allocation Problem

Hi All

I am creating a huge 3D array of size 700 by 200 by 200 having
instances of one of my class. I use the following code to create it.

voxelCube_ = new Voxel**[xBound_];

for( int m=0; m<xBound_; m++)
{
voxelCube_[m] = new Voxel*[yBound_];
for (int l=0; l<yBound_; l++)
{
voxelCube_[m][l]= new Voxel[zBound_];
}
}

However after certain limit the program assigns value NULL to the
pointer. I am not sure why this is happening. Please let me know if
anybody has any idea about this phenomenon.

Regards

Nikhil

nvjoglekar wrote:

> Hi All
>
> I am creating a huge 3D array of size 700 by 200 by 200 having
> instances of one of my class. I use the following code to create it.
>
> voxelCube_ = new Voxel**[xBound_];
>
> for( int m=0; m<xBound_; m++)
> {
> 	voxelCube_[m] = new Voxel*[yBound_];
> 	for (int l=0; l<yBound_; l++)
> 	{
> 		voxelCube_[m][l]= new Voxel[zBound_];
> 	}
> }
>
> However after certain limit the program assigns value NULL to the
> pointer. I am not sure why this is happening. Please let me know if
> anybody has any idea about this phenomenon.

Sounds like your C++ implementation is broken. 'new' may not return a
null pointer. Some implementations incorrectly return a null pointer
when the request cannot be fulfilled.

Also, If you need a massive 3-dimensional array then your algorithm is
probably broken.

-Kevin
--
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To contact me please use the address from a recent posting.

* nvjoglekar@rediffmail.com (nvjoglekar) schriebt:
>
> I am creating a huge 3D array of size 700 by 200 by 200 having
> instances of one of my class. I use the following code to create it.
>
> voxelCube_ = new Voxel**[xBound_];
>
> for( int m=0; m<xBound_; m++)
> {
> 	voxelCube_[m] = new Voxel*[yBound_];
> 	for (int l=0; l<yBound_; l++)
> 	{
> 		voxelCube_[m][l]= new Voxel[zBound_];
> 	}
> }

When you need such a "huge" thing (what is huge and what is small is
often very system-dependent) the size is often known in advance.  So
you can then use a single stack-based variable or dynamic allocation
of _one_ large variable.



> However after certain limit the program assigns value NULL to the
> pointer. I am not sure why this is happening. Please let me know if
> anybody has any idea about this phenomenon.

Pre-standard behavior, e.g. in Visual C++ 6.0.  Simply do



#include <stdexcept>

..

template<typename T>
inline T* notNull( T* p ){ if( !p ){ throw std::bad_alloc(); } ret
urn p; }

..

voxelCube_ = ::notNull( new Voxel**[xBound_] );

for( int m=0; m<xBound_; m++)
{
voxelCube_[m] = ::notNull( new Voxel*[yBound_] );
for (int l=0; l<yBound_; l++)
{
voxelCube_[m][l]= ::notNull( new Voxel[zBound_] );
}
}


And do _not_ listen to anyone who wants you to install a "new-handler"
which changes the behavior of operator new, because that might break a lot
of libraries that you're implicitly using, including the run-time lib.

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