Don't have enough memory

This is a discussion on Don't have enough memory within the C++ Programming forums, part of the General Programming Boards category; Hi to everyone. I have a little program and my compiler desn't allocate enough memory for a matrix. Code: include ...

  1. #1
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    Don't have enough memory

    Hi to everyone. I have a little program and my compiler desn't allocate enough memory for a matrix.

    Code:
    include <iostream>
    #include <fstream>
    using namespace std;
    int main()
    {
        int i, j, a[1001][1001], x, y, t1, t2, s1, s2, s3, s4, r1, r2, r3, r4, k, n;
    
        fstream f("ai.in.TXT", ios :: in);
    
        f>>n>>t1>>t2>>s1>>s2>>s3>>s4>>r1>>r2>>r3>>r4>>k;
    
        cout<<n<<t1<<t2<<s1<<s2<<s3<<s4<<r1<<r2<<r3<<r4<<k;
    
    }
    I'm using Code :: Blocks. What can i do for gain more memory ?

  2. #2
    C++ Witch laserlight's Avatar
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    Use a std::vector instead, either as a vector of vector, or by having a huge vector that you divide into chunks.
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    @laserlight how can i do that ?

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    C++ Witch laserlight's Avatar
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    For the former, it means using:
    Code:
    std::vector<std::vector<int> > a(1001, std::vector<int>(1001));
    Remember to #include <vector>. You can then use the same array index syntax that you have been using. The idea is that the memory allocated will likely have a larger upper limit than if you used a local array.

    By the way, you should give your variables descriptive names.
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    I will have to read more about your idea. Thank you for the advice, but is a way to set my compiler to allocate more memory for that matrix ?

  6. #6
    and the hat of wrongness Salem's Avatar
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    No one in their right mind dumps a 4MB array on the stack.

    Yes there is a way to increase the default stack size, but it is VERY dependent on your operating system. In some environments, you're simply not allowed to increase the default stack size, so picking a better method is just an all-round good idea.

    static int arr[1000][1000];
    would take it off the stack, but would still be a big waste of space.

    Ideally, you find out how big it really needs to be at run-time, and allocate accordingly.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    C++まいる!Cをこわせ! Elysia's Avatar
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    Not to mention there is a limit to how much the OS and compiler will allow you to put on the stack, and it's rather low. I think I can fairly well predict you can't get more than 10 MB--maximum. You will probably get much less than that usually. The default stack size in Windows is 1 MB.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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