ISO C Random Number Functions

最新推荐文章于 2025-08-23 15:05:11 发布

weixin_30617695

最新推荐文章于 2025-08-23 15:05:11 发布

阅读量63

点赞数

CC 4.0 BY-SA版权

文章标签：操作系统

原文链接：http://www.cnblogs.com/xiaoxiaoxin-love-ping/p/3528861.html

本文介绍了ISO C标准中定义的随机数生成函数，包括rand()和srand()等，并解释了如何使用这些函数来生成伪随机数序列。此外，还提到了POSIX.1扩展的rand_r()函数，用于支持多线程程序中的可重现随机数。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

This section describes the random number functions that are part of the ISO C standard.

To use these facilities, you should include the header file `stdlib.h' in your program.

Macro: int RAND_MAX

The value of this macro is an integer constant representing the largest value the rand function can return. In the GNU library, it is 2147483647, which is the largest signed integer representable in 32 bits. In other libraries, it may be as low as 32767.

Function: int rand (void)

The rand function returns the next pseudo-random number in the series. The value ranges from 0 to RAND_MAX.

Function: void srand (unsigned int seed)

This function establishes seed as the seed for a new series of pseudo-random numbers. If you call rand before a seed has been established with srand, it uses the value 1 as a default seed.

To produce a different pseudo-random series each time your program is run, do srand (time (0)).

POSIX.1 extended the C standard functions to support reproducible random numbers in multi-threaded programs. However, the extension is badly designed and unsuitable for serious work.

Function: int rand_r (unsigned int *seed)

This function returns a random number in the range 0 to RAND_MAX just as rand does. However, all its state is stored in the seed argument. This means the RNG's state can only have as many bits as the type unsigned int has. This is far too few to provide a good RNG.

If your program requires a reentrant RNG, we recommend you use the reentrant GNU extensions to the SVID random number generator. The POSIX.1 interface should only be used when the GNU extensions are not available.

转载于:https://www.cnblogs.com/xiaoxiaoxin-love-ping/p/3528861.html