How to know the right max size of vector? max_size()? but no

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When using vector, "Out of Memory" show. To fix it, I use max_size() to check, then reserve or push_back. If the max_size() is bigger the reserved value, it should be ok, but it is no! Then what's the meaning of max_size()? I compile below demo in windows 7 and Visual studio 2010. My PC has 4GB RAM. When the reseverd is 1/2 of max_size(), it fails.

max_size()=2^32/sizeof(CPoint3D)-1=268435455

It's ok when 1/4 of max_size() in the demo. In my real project, It's ok until 1/10.

What's the right of max size of vector, how to enlarge it?


I got the "out of memory" error when I push a lot of elements into std::vector. To avoid the error, I checked with vector::max_size() first, and use vector::reserve() to pre-allocate the memory. However, it doesn't work. In a demo project, the error occurs when I reserve 1/4 of the max_size. In the real project, the error occurs when I reserve 1/10 of it. I'm running Windows 7 and compiling with Visual Studio 2010. My computer has 4GB RAM.

If max_size doesn't work, how do I find out the maximum number of elements I can allocate for a vector?


The problem is that vector tries to allocate a contiguous block of memory, which might not be available at that time, even though the total available memory may be much larger.

I would suggest to use std::deque as it does not require to allocate a contiguous block of memory.

c++, max_size() tells you the design limit of the class, but memory shortage can limit the real size to something smaller. There's not generally any way to find what the � The vector::max_size() is a built-in function in C++ STL which returns the maximum number of elements that can be held by the vector container. Syntax: vector_name.max_size() Parameters: The function does not accept any parameters. Return value: The function returns the maximum numbers that can fit into the vector container.


max_size() tells you the design limit of the class, but memory shortage can limit the real size to something smaller. There's not generally any way to find what the lower limit might be though (e.g., it might change from one moment to another, depending on how much memory is used by other programs).

std::vector::max_size, This is the maximum potential size the container can reach due to known system or library implementation limitations, but the container is by no means comparing size, capacity and max_size #include <iostream> #include <vector> int main () { std::vector< int > cplusplus.com, 2000-2020 - All rights reserved - v3.2 Returns the maximum number of elements that the vector can hold. This is the maximum potential size the container can reach due to known system or library implementation limitations, but the container is by no means guaranteed to be able to reach that size: it can still fail to allocate storage at any point before that size is reached.


max_size() returns the maximum number of elements a vector can possibly hold. That is, the absolute limit when taking into account things like the addressing limits using the integral types it might store and the address space limits of the operating system.

This doesn't mean you can actually make a vector hold that many elements. It just means you can never store more. Also just because you have 4 gigs of RAM doesn't mean you can actually create a single contiguous buffer that occupies 4 gigs of RAM or anywhere close. There are other factors to consider like memory fragmentation (you might only be able to page a one gig memory block into physical memory due to it).

If you really need this many elements in a container, a contiguous sequence is probably not a good choice. For data sets that large, you may need something that can be paged in bits and pieces like std::deque.

vector::size - C++ Reference, vector::size #include <iostream> #include <vector> int main () { std::vector< int > myints No contained elements are accessed: concurrently accessing or modifying them is safe. See also. vector::capacity: Return size of allocated storage capacity (public vector::max_size: Return maximum size (public member function )� Given a vector, find the maximum element of this vector using STL in C++. Example: Input: {1, 45, 54, 71, 76, 12} Output: 76 Input: {1, 7, 5, 4, 6, 12} Output: 12


vector::capacity() gives the maximum number of elements that can be stored in the vector without having a re-allocation, one which can potentially fail from std::bad_alloc.

vector::max_size() has a different meaning, roughly similar to (INT_MAX / sizeof(element)).

For more information on Windows memory management, see the MSDN article

vector max_size() function in C++ STL, The vector::max_size() is a built-in function in C++ STL which returns the maximum number of elements that can be held by the vector container. Syntax: vector_name.max_size(). Parameters: The function does not accept any parameters. See your article appearing on the GeeksforGeeks main page and � No contained elements are accessed: concurrently accessing or modifying them is safe. Exception safety No-throw guarantee: this member function never throws exceptions. See also vector::capacity Return size of allocated storage capacity (public member function ) vector::resize Change size (public member function ) vector::max_size


std::vector<bool>, vector::max_size std::vector<bool> behaves similarly to std::vector, but in order to be space efficient, it: Does not necessarily store its elements as a contiguous array. returns the maximum possible number of elements If the size of the bitset is known at compile time, std::bitset may be used, which� size() – Returns the number of elements in the vector. max_size() – Returns the maximum number of elements that the vector can hold. capacity() – Returns the size of the storage space currently allocated to the vector expressed as number of elements. resize(n) – Resizes the container so that it contains ‘n’ elements.


What is the maximum size of an vector<>::maxsize()?, What is the maximum size of an vector<>::maxsize()? - c++ So just run this and check out the answer for your system. However in practice the There's no limit except the available memory. But: a But max_size is nothing. After it Then get the intermediate mid_t size correct so that expensive reallocations are rare. Vector has an implementation-specific upper limit on its size, but you are likely to run out of RAM before reaching it: vector<int> v; const vector<int>::size_type max_size = v.max_size(); cout << max_size << endl; // prints some large number v.resize( max_size ); // probably won't work v.push_back( 1 ); // definitely won't work Common mistake


How to compare 2D vector size with OS memory address limitations , Here is the previous question where I and others solved that problem: Vector of vector storage limitations Determine the max size of the memory allocation with I know unlike array there is no limit on vectors. Here vector<bool>::max_size () will be the correct limit. What is the maximum size of an vector<>::maxsize()?. Following is the declaration for std::vector::size() function form std::vector header. C++98 size_type size() const; C++11 size_type size() const noexcept; Parameters. None. Return value. Returns the actual objects present in vector, which may be differ than storage capacity of vector. Exceptions. This member function never throws exception