Question

I am new to coding C++ in Xcode as my framework so I would like to ask a question that I believe is merely related to memory management

What I’m trying to achieve is that I try to create a matrix size 10000 x 10000 however even I do the proper coding(at least that’s what I believe) I just can’t get it to work, just pointing out the EXC_BAD_ACCESS error.

You can find my code in below. Is this an XCode-oriented error or I’ve done an obvious coding error?

#include <iostream>
using namespace std;

    int main(int argc, const char * argv[])
    {

        // insert code here...
        int matrix[10000][10000];
        for(int i=0;i<10000;i++)
            for(int j=0;j<10000;j++)
                matrix[i][j]=24;
        cout<<"Done"<<endl;
        return 0;
    }

Answer 1

If Jesse Good posts his comment “int matrix[10000][10000]; looks like a stack overflow to me. ” as an answer, I’ll delete this.

You should create an allocation of this size on the heap, rather than on the stack.

Here’s the breakdown:

400,000,000 bytes = 10000*10000*sizeof(int)

One common way to overcome this problem by creating allocations on the heap would be:

#include <iostream>
#include <vector>

int main(int argc, const char* argv[]) {
    std::vector<std::vector<int> > matrix(10000, std::vector<int>(10000, 24));
    cout<<"Done"<<endl;
    return 0;
}

Stack size is determined by the operating system, hardware, and other things. You may have less than one MB to work with, but not usually more than a few. Therefore, large stack allocations should be avoided.