Why Does rand() Generate the Same Numbers, and How Can I Fix It?

Solving Non-Random rand() Behavior

When executing programs utilizing the rand() function, users frequently encounter the issue of obtaining consistent numerical sequences. This article investigates the source of this behavior and proposes a solution to ensure true randomness.

The rand() function generates pseudorandom numbers, which are not inherently random but rather based on specific algorithms. These algorithms undergo mathematical transformations using a seed or previous random numbers, which results in the observed non-randomness.

To overcome this issue, we need to set a random seed for the random number generator. This can be achieved using the srand() function with an argument based on system time or other non-deterministic sources. By initializing the seed with a different value each time, we effectively reset the random number generation algorithm, ensuring a more random outcome.

Consider the following example:

#include <iostream>
#include <cstdlib>
#include <ctime>

int main() {
    srand((unsigned int)time(NULL));
    std::cout << rand() << std::endl;
    return 0;
}

In this example, we use srand() with a seed derived from the current system time. As the system time continuously changes, the random number sequence will also vary, leading to true randomness.

For further insights into the concept of pseudorandom number generators, refer to the provided links:

• http://www.dreamincode.net/forums/topic/24225-random-number-generation-102/
• http://www.dreamincode.net/forums/topic/29294-making-pseudo-random-number-generators-more-random/

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