Why is `rand()` Considered a Poor Choice for Random Number Generation in C?

Why is rand() Considered Bad Practice?

Despite the use of a seed with srand(), the usage of rand() is often discouraged due to inherent limitations and the quality of its implementation.

Pseudorandom Number Generation:

Rand is a pseudorandom number generator, meaning it relies on a seed to generate a sequence of numbers. This sequence is repeatable if the same seed is used. While sufficient for some applications, it may not provide adequate randomness for security-critical scenarios where predictability is undesirable.

C Random Library Shortcomings:

Beyond its pseudorandom nature, the C random library suffers from several shortcomings:

• Global State: The seed set by srand() is shared across the program, making concurrent use of multiple random engines impossible. This also complicates multithreaded tasks.
• Lack of Distribution Engine: Rand produces numbers uniformly within a limited range ([0, RAND_MAX]). For generating numbers in custom intervals or with specific distributions, additional calculations are necessary, potentially compromising uniformity.
• Poor Implementation: The implementation of rand() varies across different platforms and compilers, resulting in inconsistent behavior and potential bias.

Alternatives for Modern C :

In modern C , the library provides a superior alternative to the rand() function. It offers a variety of random number engines with well-defined properties and distribution mechanisms for both integer and floating-point types. These engines allow for fine-grained control over randomness and ensure more consistent and robust results.

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