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App Inventor 2 蓝牙发送十六进制字节方案:文本转Hex字节详解 - App应用开...

问题描述用户在文本框输入"ABCD",想通过蓝牙发送 0xAB 0xCD 两个字节,而不是四个ASCII字符(0x41 0x42 0x43 0x44)。 每两个字符代表一个十六进制字节,需要将字符对解析为实际的字节值。 问题本质输入期望发送实际发送...
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kernel stack and user space stack

...sable, and therefore will require one set under its own control. Different CPU architectures implement this in different ways; x86 CPUs automatically switch stackpointers when privilege mode switches occur, and the values to be used for different privilege levels are configurable - by privileged cod...
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从一个开发的角度看负载均衡和LVS - 更多技术 - 清泛网 - 专注C/C++及内核技术

...允许的情况下我们会采用软负载,软负载解决的两个核心问题是:选谁、转发,其中最著名的是LVS(Linux Virtual Server)。 三、软负载——LVS LVS是四层负载均衡,也就是说建立在OSI模型的第四层——传输层之上,传输层上有...
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为什么我们程序员写不出好代码? - 杂谈 - 清泛网 - 专注C/C++及内核技术

...提交的仓库里。如果代码行数都计算在内的话,原本一个问题只需10行代码即可解决,程序员有可能编写5000行代码,来让功能更加灵活和兼容,这样,他的代码总量就会增加5000行了。 衡量生产力反而会使代码变的更糟,让项目...
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Compiled vs. Interpreted Languages

...e. Or let's say: There are native compilers (creating machine code for the CPU to eat), and not-so-native-compilers (creating tokenized stuff, i.e. intermediate code, that some just-in-time compiler compiles to machine code before (or during) runtime ONCE), and there are "real" non-compilers that ne...
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Why doesn't C have unsigned floats?

...d floats is because there is no equivalent machine code operations for the CPU to execute. So it would be very inefficient to support it. If C++ did support it, then you would be sometimes using an unsigned float and not realizing that your performance has just been killed. If C++ supported it ...
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How to benchmark efficiency of PHP script

...rces become scarce. This raises another question: are you bottlenecking on CPU? RAM? I/O? You also need to look beyond just the code you are running in your scripts to how your scripts/pages are being served. What web server are you using? As an example, I can make nginx + PHP-FPM seriously out per...
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Why does multiprocessing use only a single core after I import numpy?

...hine- and task-specific . Update: There are also two ways to disable the CPU affinity-resetting behaviour of OpenBLAS itself. At run-time you can use the environment variable OPENBLAS_MAIN_FREE (or GOTOBLAS_MAIN_FREE), for example OPENBLAS_MAIN_FREE=1 python myscript.py Or alternatively, if you...
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Virtual functions and performance - C++

...curious, so I went ahead and ran some timings on the 3GHz in-order PowerPC CPU we work with. The test I ran was to make a simple 4d vector class with get/set functions class TestVec { float x,y,z,w; public: float GetX() { return x; } float SetX(float to) { return x=to; } // and so on...
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Difference between a “coroutine” and a “thread”?

...ple threads may be executing at any given time. (Traditionally, on single-CPU, single-core machines, that concurrency was simulated with some help from the OS -- nowadays, since so many machines are multi-CPU and/or multi-core, threads will de facto be executing simultaneously, not just "conceptual...