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C#: Virtual Function invocation is even faster than a delegate invocation?

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It just happens to me about one code design question. Say, I have one "template" method that invokes some functions that may "alter". A intuitive design is to follow "Template Design Pattern". Define the altering functions to be "virtual" functions to be overridden in subclasses. Or, I can just use delegate functions without "virtual". The delegate functions is injected so that they can be customized too. Originally, I thought the second "delegate" way would be faster than "virtual" way, but some coding snippet proves it is not correct. In below code, the first DoSomething method follows

Mongoose virtual fields included in toJSON by default: schemaOptions.toJSON.virtuals = true; still doesn't include virtual fields by default

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问题 I saw in another answer that in order to include the virtual fields you must do like https://groups.google.com/forum/?fromgroups#!topic/mongoose-orm/HjrPAP_WXYs var schemaOptions = { toJSON: { virtuals: true } }; which I've done; Now in the Schema: new Schema({...}, schemaOptions); But still so, the data doesn't include the virtual.. :s But like this works: var docsCallback = function(err, docs){ var i = docs.length; var nDocs = []; while(i--){ nDocs[i] = docs[i].toObject({virtuals: true}); }

How to calculate page table size?

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问题 Given : 64 bit virtual byte address, 16 KB pages, 32-bit physical byte address. What is the total size of page table on this machine, assuming that the valid, protection, dirty and use bits take a total of 4 bits and all virtual pages are in use. So far I know the total number of page table entries : 2^64 / 2^14 = 2^50, but am not able to understand how to find the size of each entry. Each entry does contain 4 bits as said in the question, but can the size rest of the entry be found from the

Is final used for optimization in C++?

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问题 class A { public: virtual void f() = 0; }; class B : public A { public: void f() final override { }; }; int main() { B* b = new B(); b->f(); } In this case, is the compiler required to still do the v-table lookup for b->f(); , or can it call B::f() directly because it was marked final ? 回答1: Is final used for optimization in C++? It can be, and is. As noted, it is being used already; see here and here showing the generated code for the override with and without final . An optimisation along

What is the easiest way to run python scripts in a cloud server?

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I have a web crawling python script that takes hours to complete, and is infeasible to run in its entirety on my local machine. Is there a convenient way to deploy this to a simple web server? The script basically downloads webpages into text files. How would this be best accomplished? Thanks! Since you said that performance is a problem and you are doing web-scraping, first thing to try is a Scrapy framework - it is a very fast and easy to use web-scraping framework. scrapyd tool would allow you to distribute the crawling - you can have multiple scrapyd services running on different servers

Is it possible to declare a virtual static constant value in a C++ class?

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I'd like to have a base class that has a constant field (like an unique ID associated with the class that can't be modified after compile time). So far the static const declaration would be just fine. Now, I'd like to inherit this base class and make sure that the children of this class do have the same field, but with their own values. How can I do this? Let's say, I'd like to have a base class called Base with an ID field that holds the int value of 0. Then, I'd like to have the classes A , B and C , all of them being public children of Base and I'd like to make sure that these children

How do I get the complete virtual path of an ASP.NET application

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问题 How do I know the the complete virtual path that my application is currently hosted? For example: http://www.mysite.com/myApp or http://www.mysite.com/myApp/mySubApp I know the application path of HttpRequest but it only returns the folder name that my application is currently hosted, but how do I get the initial part? 回答1: The domain name part of the path is not really a property of the application itself, but depends on the requesting URL. You might be able to reach a single Web site from

Understanding virtual address and virtual address space

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问题 I read that , "When a program executes an instruction like : MOV REG,1000 , it does so to copy the contents of the memory address 1000 to REG. Address can be generated using indexing,base registers,segment registers and other ways. These program generated address are called virtual address and form the virtual address space." Can anyone please explain me,what does it (These program generated address are called virtual address) mean ? 回答1: Programs and data are stored as numbers in memory

What things (or in what cases) can make C++ slower than C ?

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This is an interview question, the interview has been done. What things can make C++ slower than C ? The interviewer asked it very deep and always asked "anything else ? " whenever I said something. My ideas: C++ features not available in C may have some cost. For example, if we use assignment to initialize class's members inside a constructor not by the initialization list, the member's default constructor may be called once before the body of the constructor, and then that value wiped out by the assignment. Virtual functions need to be called by searching virtual function pointer. This is a

Android Virtual Device on Windows 10 - Endless “VCPU shutdown request” - doesn't launch

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可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: My x86 AVDs never load. I've searched all over for a solution but haven't seen a solution that has worked for me. Configuration OS: Windows 10 Home RAM: 12 GB CPU: Intel Core i5-7200 CPU Supports VT-x, EM64T,and XD Bit as required by HAXM (per Intel specs) HAXM version: 6.0.4 Android Studio version: 2.2 Bios: Insyde F.21 Bios config: Virtualization Technology enabled. Steps 1. In Android Studio, launch Android Virtual Device Manager. 2. Create Nexus 5 API 24 AVD with all default settings. 3. Launch the AVD. Results: AVD window displays. No