Crash on compiling an array of arrays when size increases

Question

I am trying to return a matrix of integers in a function and I decided to go with a typdef form of matrix. But when I run the project with a function that return a matrix size of 1500 by 1500, the compilation crashed after the project was built. Then I tried to work with different matrix sizes and when I compiled a the code I pasted here with a smaller size (150) for defined Matrix, the problem was solved. This is what I have tested with no problem.

typedef int Matrix[150][150];

int main(){
Matrix mat;
for(int i=0;i<13;i++){
    for(int j=0;j<13;j++){
        mat[i][j]=i;
    }
}
cout << mat[10][11];
return 0;
}

The size of 1500 by 1500 seems very small and I cannot figure out what is the problem it is causing.

Here is the error image:

Answer 1

That matrix gets allocated on the stack , which is only few MB by default. 1500*1500*4 takes up about 9MB. Large arrays like that are best allocated on the heap (new/delete).

Answer 2

A 1500 x 1500 matrix of ints would be nearly 9MB with 32-bit ints or nearly 18MB with 64-bit ints. That's an enormous stack allocation, and you'er probably hitting a compiler or environment limit. There may be some build-time flags that could address the issue, but a more reasonable solution would be to allocate the object on the heap with new

Answer 3

You're probably running out of stack space - 1500*1500*sizeof(int) is roughly 9 megabytes on a 32 bit system, for example. Use an std::vector or such (it allocates from the heap) or else look up the necessary switch for your compiler to increase your stack size...