随机数发生器 - 种子为什么每次 [英] Random number generator - why seed every time

问题描述

我是相对新的C和C ++。在Java中，我使用的语言进行编程中，其很容易实现的随机数生成。只需调用从名为Math类的静态随机方法。

I am relative new to c and c++. In java, the language I am used to program in, its very easy to implement random number generation. Just call the the static random-method from a class called Math.

int face = ((int)(Math.random() * 6) + 1);

的模拟一个骰子掷... 的

在C和C ++，你必须的种子随机数生成器的，通过调用函数srand功能

In c and c++ you have to "seed the random number generator" , by calling the srand-function

srand ( time(NULL) );

什么是做这点 - ？有我的意思是有每次code运行时种子随机数发生器的任何优势。

What is the point of doing this - I mean is there any advantage of having to seed the random number generator every time the code is run?

推荐答案

给定同样的种子，一个伪随机数发生器，每次将产生相同的序列。所以它归结为是否要伪随机数的不同的序列每次运行，还是不行。

Given the same seed, a pseudo random number generator will produce the same sequence every time. So it comes down to whether you want a different sequence of pseudo random numbers each time you run, or not.

这真的取决于你的需要。还有，当你要重复序列倍。当你做几次都不。您需要了解每一个具体应用的需求。

It really depends on your needs. There are times when you want to repeat a sequence. And times when you do not. You need to understand the needs of each specific application.

有一件事必须永远不会做代单个序列的过程中反复种子。这样做很可能会破坏你的序列分布情况。

One thing you must never do is seed repeatedly during generation of a single sequence. Doing so very likely will destroy the distribution of your sequence.

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