Why Does My rand() Function Produce the Same Random Number Sequence Every Time?

Understanding the Predictability of rand() Sequences

Problem Statement:
In a program utilizing the rand() function, users encounter consistent sequences of random numbers across multiple runs, making the results appear non-random.

Answer:
The consistency in rand() results stems from an uninitialized seed for the random number generator. By default, rand() uses the same seed upon each program execution, leading to the predictable number sequences.

Solution:
To address this issue, the program should initialize the seed using a truly random value. One common approach is to utilize the srand() function with an argument based on the system time:

srand((unsigned int)time(NULL));

This assignment ensures that the seed changes with each program run, resulting in more random number sequences.

Technical Explanation:
The rand() function operates as a pseudorandom number generator (PRNG). PRNGs are deterministic algorithms that, given the same seed, will always produce the same sequence of numbers. Without a proper initialization, rand() starts with a predefined seed, leading to the repetition of sequences.

Additional Resources:

• [Understanding Pseudorandom Number Generation](http://www.dreamincode.net/forums/topic/24225-random-number-generation-102/)
• [Enhancing the Randomness of PRNGs](http://www.dreamincode.net/forums/topic/29294-making-pseudo-random-number-generators-more-random/)

The above is the detailed content of Why Does My rand() Function Produce the Same Random Number Sequence Every Time?. For more information, please follow other related articles on the PHP Chinese website!