Problem with const int.

[ritika_sharma82]

Sorry to ask simple question, but, even after googling I couldn't solve my problem. Hope you guys can help me.

const int i=100000;
const int j=32;
__int64 A[i][j];
...

It compiles but when I run the .exe file it gives an error. The error is like:

.exe has encountered a problem and needs to close. We are sorry for the inconvenience. ....... Send error report/Don't send.

But, when I decrease one zero in i's value (i.e. when const int i=10000 it works fine.
What is the problem here and how can I solve it?
Thank you.

[GCDEF]

You're probably running out of stack space.

[ritika_sharma82]

You're probably running out of stack space.

Hi GCDEF,
How can I solve it.
Any quick and easy solution will be appreciated.
I am using MS Visual c++ 6.0

[JohnW@Wessex]

Is this a local variable?
If so, you are trying to allocate 25,600,000 bytes on the stack.
(100000 * 32 * 8)
That is highly unlikely to work on any machine! The default on Windows machines is 1MB per thread (I think).

You will have to allocate from the heap, either with a 'new' or use a std::vector.

[ritika_sharma82]

Is this a local variable?
If so, you are trying to allocate 25,600,000 bytes on the stack.
(100000 * 32 * 8)
That is highly unlikely to work on any machine! The default on Windows machines is 1MB per thread (I think).

You will have to allocate from the heap, either with a 'new' or use a std::vector.

Hello JohnW,
These are the local variables. Could you please give me an example? How to use heap?
My array is exactly A[100000][3]. So, it comes (100000 * 3 * 8)/(1024*1024) = 2.28MB.

[JohnW@Wessex]

Using std::vector

#include <vector>

using namespace std;

int main()
{
    const int i = 100000;
    const int j = 32;

    vector<vector<__int64>> A(i, vector<__int64>(j));
}

Though if you are going to have large 2D arrays then it is often better to wrap a 1D vector in a class and let the interface emulate the 2D aspect. In that way there is only one allocation of memory and a lot less heap fragmentation.
You can write your own fairly simply or Use Boost's multi_array.