swap | 易学教程

How is std::vector::swap implemented?

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问题 It occurred to me that the fastest way to copy the array from one std::vector to another would be to swap their pointers, as long as you don't care anymore about the vector you are swapping from. So I went looking and found std::vector::swap . I assume that swapping pointers is how its implemented, but I didn't see an explanation in the reference. 回答1: A simplified, minimal vector implementation might have something like the following members to manage the data in the vector: template

ECS Linux如何增加虚拟内存swap

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由于开启swap分区会导致硬盘IO性能下降，因此阿里云服务器初始状态未配置swap，如果某些应用需要开启swap分区，可以采用如下方法增加： 1、创建用于交换分区的文件 #dd if=/dev/zero of=/mnt/swap bs=block_size count=number_of_block 注： block_size、 number_of_block 大小可以自定义，比如bs=1M count=1024 代表设置1G大小swap分区 2、设置交换分区文件 #mkswap /mnt/swap 3、立即启用交换分区文件 #swapon /mnt/swap 如果在/etc/rc.local中有 swapoff -a 需要修改为 swapon -a 4、设置开机时自启用swap分区需要修改文件/etc/fstab中的swap行。添加 /mnt/swap swap swap defaults 0 0 注：/mnt/swap 路径可以修改，可以根据创建的swap文件具体路径来配置。设置后可以执行free -m命令查看效果来源： oschina 链接： https://my.oschina.net/u/1767904/blog/620850

-Wsequence-point warning - what does it mean and does it violate ANSI C standard?

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问题 In line tab[i] = tab[i+1] - tab[i] + (tab[i+1] = tab[i]); I have a warning [Warning] operation on '*(tab + ((sizetype)i + 1u) * 4u)' may be undefined [-Wsequence-point] I want to swap these two integer arrays elements without temporary variable and without violation of ANSI C. Program still works, but is it ok? 回答1: Your code relies on behaviour that is not covered by the standard. So your code may behave differently on different compilers, different versions of the same compiler and even

How do I get an object to move and swap places with another object, on a mouse clic

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问题 I have a script so far that moves an object a small distance upon a mouse click, however I want to change it so that when I click this object, it swaps places with another obejct next to it, instead of just the small distance it is moving now. I am a little confused on how to do this, because I am new to unity. using UnityEngine; using System.Collections; public class NewBehaviourScript: MonoBehaviour { public float movementSpeed = 10; void Update(){ if ( Input.GetMouseButtonDown(0)) {

What's the efficient way to swap two register variables in CUDA?

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问题 I'm starting to write some CUDA code, and I want to do the equivalent of std::swap() for two variables within a kernel; they're in the register file (no spillage, not in some buffer, etc.). Suppose I have the following device code: __device__ foo(/* some args here */) { /* etc. */ int x = /* value v1 */; int y = /* value v2 */; /* etc. */ swap(x,y); /* etc. */ } Now, I could just write template <typename T> void swap ( T& a, T& b ) { T c(a); a=b; b=c; } but I wonder - isn't there some CUDA

Swapping with rvalues

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问题 Suppose I want swap that works on rvalues, and don't want to write 4 versions for all combinations of rvalue/lvalue references (rvalue/rvalue version is kinda pointless but it doesn't hurt). I came up with this: template <typename A, typename B> struct is_same_no_ref : std::is_same< typename std::remove_reference<A>::type, typename std::remove_reference<B>::type > {}; template <typename A, typename B, typename = typename std::enable_if<is_same_no_ref<A, B>::value>::type > inline void my_swap

Swapping with rvalues

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Add swap memory with ansible

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问题 I'm working on a project where having swap memory on my servers is a needed to avoid some python long running processes to go out of memory and realized for the first time that my ubuntu vagrant boxes and AWS ubuntu instances didn't already have one set up. In https://github.com/ansible/ansible/issues/5241 a possible built in solution was discussed but never implemented, so I'm guessing this should be a pretty common task to automatize. How would you set up a file based swap memory with

Swap the first two element of a list, (Haskell)

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问题 In order to swap the first two elements of a list, I've written the following code: swap_first_two_elements :: [a]->[a] swap_first_two_elements list=case list of x:y:_ -> y:x:_ [x] -> Nothing []-> Nothing However, the terminal shows the error shown below: [1 of 1] Compiling Main ( test.hs, interpreted ) test.hs:3:16: Pattern syntax in expression context: _ Failed, modules loaded: none. Prelude> Who likes to tell me what is wrong with it? Btw, ive also tried to combine the last two row into:

Swap two values in a numpy array.

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问题 Is there something more efficient than the following code to swap two values of a numpy 1D array? input_seq = arange(64) ix1 = randint(len(input_seq)) ixs2 = randint(len(input_seq)) temp = input_seq[ix2] input_seq[ix2] = input_seq[ix1] input_seq[ix1] = temp 回答1: You can use tuple unpacking. Tuple unpacking allows you to avoid the use of a temporary variable in your code (in actual fact I believe the Python code itself uses a temp variable behind the scenes but it's at a much lower level and