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Dovyman

really big arrays?

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For some reason this: int fractal_set[1024][768]; generates an immediate page fault at runtime using MS VCPP 2k3 and Win32 base code. But the same thing does not create any problems if I use it in a console application... whats going on? and how do I fix it?

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Quite simply, the stack is a very limited resource. So you can't allocate large arrays on it. As was already said in the previous thread before you deleted it, use new/malloc or std::vector.

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Stack overflow (1MB by default in VS, your array is precisely 3MB). Either make a bigger stack (not a good idea) or dynamically allocate your array: int *fractal_set = new int[1024*768]; or std::vector<int> fractal_set(1024*768);
No, you are not getting "2D indexing" - get over it (index = x+768*y)

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You are blowing the stack. Try allocating it dynamically with new or free and see how it goes.

[edit] Wow, almost simultaneous answers.

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Really big arrays (or any other large data type) should be allocated on the heap (using new, malloc or whatever your allocation method of choice is) instead of the stack. You can also cover up the symptoms by increasing the stack size in the linker options, but this tends to scale poorly.

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big arrays you typically want to put on the heap as it has much more space:


int *fractal_set = new int[1024*768];



sadly you cannot nicely access multi-dimensional arrays that are declared on the heap. so you have to access it by:


//this is the equivalent of [x][y]
fractal_set[y*768 + x];



if you really want to keepit on the stack, you can increase the default stack space size that you are given somehow... though i forget.

-me

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Is the 3MB array on the heap or the stack?
Can you post some minimal amount of code which reproduces the problem?
It's not the declaration that causes the problem btw, it's the code that accesses it.

OMG lets just all post at once - LOL!

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Quote:
Original post by iMalc
It's not the declaration that causes the problem btw, it's the code that accesses it.


Actually, it is the declaration that causes the problem.

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Assume an int is 4 bytes; 4*1024*768 is over 3000000 bytes. That's 3MB. The stack cannot take that much. [smile]

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