C++17 added std::hardware_destructive_interference_size and std::hardware_constructive_interference_size . First, I thought it is just a portable way to get the size of a L1 cache line but that is an oversimplification. Questions: How are these constants related to the L1 cache line size? Is there a good example that demonstrates their use cases? Both are defined static constexpr . Is t
C ++ 17增加了std::hardware_destructive_interference_size和std::hardware_constructive_interference_size 。 首先，我认为这只是获得L1缓存线大小的便携式方法，但这太简单了。 问题： 这些常量如何与L1缓存行大小相关？ 有没有一个很好的例子来演示他们的用例？ 两者都被定义为static constexpr 。 如果您构建二进制文件并在具有不同缓存行大小的其他机器上执行它，那么这不是问题吗？ 如果您不确定代码将运行在
I have vector of pair like this - std::vector < std::pair < int /Val1/, int /Val2/ > > myVector; What is the efficient way to compare for each pair in 'myVector' first and second element of pair (Val1 and Val2) are same or not. The only way I could think of is - bool IsFirstAndSecondSame(vector<pair<T, T>> myVector) { for(auto valuePair : myVector) {
我有像这样的对 - std :: vector <std :: pair <int / Val1 /，int / Val2 />> myVector; 对'myVector'中第一个和第二个元素（Val1和Val2）中的每对进行比较的有效方法是相同还是不相同。 我能想到的唯一方法是 - bool IsFirstAndSecondSame(vector<pair<T, T>> myVector) { for(auto valuePair : myVector) { if(valuePair.first != valuePair.second) return
I came across this code segment where two vectors are merged where elements from one vector is favored in case of duplication: std::vector<String> fields1 = fieldSource1.get(); std::vector<String> fields2 = fieldSource2.get(); // original fields1.insert(std::end(fields1), std::begin(fields2), std::end(fields2)); std::stable_sort(std::begin(fields1), std::end(fields1)); fields1.erase(
我遇到了两个向量合并的代码段，其中一个向量的元素在重复情况下受到青睐： std::vector<String> fields1 = fieldSource1.get(); std::vector<String> fields2 = fieldSource2.get(); // original fields1.insert(std::end(fields1), std::begin(fields2), std::end(fields2)); std::stable_sort(std::begin(fields1), std::end(fields1)); fields1.erase(std::unique(std::begin(fields1), std::end(fields1)), std
Using reserve() followed by push_back() 's may be faster than resizing the vector and later performing assignments -- as seen in std::vector reserve() and push_back() is faster than resize() and array index, why?. However, if I make assignments instead of using push_back() , the size of the vector remains 0 : # include <vector> int main() { std::vector<int> x; x.reserv
使用reserve()后跟push_back()的方法可能会比调整矢量大小和后续执行的任务要快 - 正如在std :: vector reserve（）和push_back（）中所看到的那样，它比resize（）和数组索引快，为什么？ 。 但是，如果我使用push_back()进行分配而不是使用push_back() ，则矢量的大小保持为0 ： # include <vector> int main() { std::vector<int> x; x.reserve(10); x[0] = 10, x[1] = 9, x[2] = 8, x[3] = 7, x[
I'm learning how to dynamically load DLL's but what I don't understand is this line typedef void (*FunctionFunc)(); I have a few questions. If someone is able answer them I would be grateful. Why is typedef used? The syntax looks odd; after void should there not be a function name or something? It looks like an anonymous function. Is a function pointer created to store the
我正在学习如何动态加载DLL，但我不明白这一行 typedef void (*FunctionFunc)(); 我有几个问题。 如果有人能回答他们，我会很感激。 为什么使用typedef ？ 语法看起来很奇怪; 在void之后应该没有函数名称或其他东西？ 它看起来像一个匿名函数。 是否创建了一个函数指针来存储函数的内存地址？ 所以我现在很困惑。 你能为我澄清事情吗？ typedef是将名称与类型关联的语言结构。 例如，您可以像使用原始类型一样
If you have a statically allocated array, the Visual Studio debugger can easily display all of the array elements. However, if you have an array allocated dynamically and pointed to by a pointer, it will only display the first element of the array when you click the + to expand it. Is there an easy way to tell the debugger, show me this data as an array of type Foo and size X? Yes, simple. s
如果您有一个静态分配的数组，Visual Studio调试器可以轻松显示所有数组元素。 但是，如果您有一个动态分配的数组并且由指针指向，那么当您单击+展开数组时，它将仅显示数组的第一个元素。 有没有一种简单的方法可以告诉调试器，将这些数据显示为Foo类型的数组和X型？ 是的，很简单。 说你有 char *a = new char[10]; 在调试器中写入： a,10 会显示内容，就好像它是一个数组。 有两种方法可以查看数组m4x4中的数据：
Basic Question: when does a program call a class' destructor method in C++? I have been told that it is called whenever an object goes out of scope or is subjected to a delete More specific questions: 1) If the object is created via a pointer and that pointer is later deleted or given a new address to point to, does the object that it was pointing to call its destructor (assuming nothing
基本问题：程序何时在C ++中调用类的析构函数方法？ 我被告知，只要对象超出范围或遭到delete ，就会调用它 更具体的问题： 1）如果该对象是通过指针创建的，并且该指针稍后被删除或指定了新的地址，那么它所指向的对象是否调用其析构函数（假设没有别的指向它）？ 2）在问题1之后，什么定义了什么时候一个对象超出了范围（而不是关于什么时候一个对象离开给定的{block}）。 换句话说，何时在链表中调用析构函数？ 3）
Lets consider following two codes First: for (int i=0;i<10000000;i++) { char* tab = new char[500]; delete[] tab; } Second: for (int i=0;i<10000000;i++) { char tab[500]; } The peak memory usage is almost the same, but the second code runs about 20 times faster than the first one. Question Is it because in first code array is stored on heap, and in the second one array i
让我们考虑以下两个代码 第一： for (int i=0;i<10000000;i++) { char* tab = new char[500]; delete[] tab; } 第二： for (int i=0;i<10000000;i++) { char tab[500]; } 峰值内存使用率几乎相同，但第二个代码的运行速度比第一个快大约20倍。 题 是否因为在第一个代码数组中存储在堆中，而在第二个数组中存储在堆栈中？ 是否因为在第一个代码数组中存储在堆中，而在第二个数组中存储在堆栈中？
Hey guys. I'm not new to programming but I am a beginner at C and C++ coding. I only know the basics of the C language and how to write small and simple programs so far. I'm not interested in learning C++ for the long haul but I am interested in becoming a fluent C programmer. My predicament is adjusting to the MS Visual Studio 2008 environment strictly for C programming (not C++). A
大家好。 我对编程并不陌生，但我是C和C ++编程的初学者。 我只知道C语言的基础知识以及如何编写迄今为止的小而简单的程序。 我对长时间学习C ++不感兴趣，但我有兴趣成为一名流利的C程序员。 我的困境是严格按照MS Visual Studio 2008环境进行C编程（而不是C ++）。 目前我只写了一些基本的C控制台应用程序，并在这个环境中构建它们。 有了这个说我会喜欢一些建议从哪里开始。 我有一些体面的C编程书籍可以学习，因此学
Possible Duplicate: What is difference between instantiating an object using new vs. without This is probably a basic question, and might have already been asked (say, here); yet I still don't understand it. So, let me ask it. Consider the following C++ class: class Obj{ char* str; public: Obj(char* s){ str = s; cout << str; } ~Obj(){ cou
可能重复： 使用new和without实例化对象有什么区别 这可能是一个基本问题，可能已经被问到（比如说）。 但我仍然不明白。 所以，让我问一下。 考虑下面的C ++类： class Obj{ char* str; public: Obj(char* s){ str = s; cout << str; } ~Obj(){ cout << "Done!n"; delete str; // See the comment of "Loki Astari" below on why this line of cod