Why are Random Numbers Repeating in Loop Iterations?

Random Number Repetition in Loop Iterations

Consider the following issue: within a loop that runs 15 iterations, the dh.setDoors() method is called. Within setDoors(), srand(time(0)) is invoked to set a seed for random number generation. Subsequently, random numbers are generated using expressions such as carSetter = rand()%3 1 or decider = rand()%2 1.

Monitoring the values of carSetter and decider reveals that they remain constant throughout each loop iteration, but change between different loop runs. This behavior is unexpected as the loop involves 15 independent iterations, suggesting that each random value should vary.

Investigating the Cause

The issue arises from the placement of srand(time(0)) at the beginning of each iteration. By resetting the seed with each loop, the sequence of pseudo-random numbers is effectively fixed by the constant value of time(0) within the iteration. As time(0) remains the same throughout the loop, the same random number sequence is generated.

Resolving the Issue

To address this problem, it is recommended to initialize the random number generator only once, at the start of the program rather than within each loop iteration. This ensures that different random number sequences are utilized for each loop iteration.

The revised implementation would resemble the following:

srand(time(0));  // Call srand() once at the start of the program

while (...) {
    x = rand();
    y = rand();
}

With this modification, the values of x and y will vary between loop iterations, producing the desired behavior of different random number sequences.

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