Examples to explain how to implement controllable probability algorithm in PHP

In computer programming, random numbers are a very important tool. In many application scenarios, we need to generate random numbers to simulate or simulate random events. Sometimes, we need to control the probability of this random event, which requires the use of a controllable probability algorithm.

PHP is a widely used programming language with strong flexibility and scalability. In PHP, we can use the rand() function to generate random numbers, but the random number generated by the rand() function is not a true random number, but a pseudo-random number. To do this, we need to use other algorithms to control the probability of occurrence of the generated random numbers.

Commonly used controllable probability algorithms include linear congruence algorithm, Fisher–Yates shuffling algorithm, Mersenne rotation algorithm, etc.

Below, we introduce the idea of ​​​​implementing a controllable probability algorithm in PHP:

1. Linear congruential algorithm

Linear congruential algorithm is a A simple random number generation algorithm that can quickly generate pseudo-random sequences. The basic idea is to generate new random numbers through a series of transformations based on the provided random number seed.

In PHP, we can use the mt_rand() function to implement the linear congruential algorithm. The random seed used by this function is generated based on the current time and can generate good pseudo-random numbers. At the same time, we can use the srand() function to set a random number seed, and use the rand() function to generate a set of random number sequences with controllable probability.

The following is a simple code example:

<?php
srand(time());
$chance = 30; //生成30%的事件
if (rand(1, 100) <= $chance) {
    // 某些操作
}
?>

In the above code, rand(1, 100) will generate a random number between 1 and 100. If the random number is less than or equal to 30, some operation will be performed. By adjusting the value of $chance, we can easily control the probability of an event occurring.

2. Fisher–Yates shuffling algorithm

The Fisher-Yates algorithm is a random permutation algorithm that can be used to generate random sequences. The algorithm is based on a very simple idea: swap elements in an array.

In PHP, we can use the shuffle() function to implement the shuffling algorithm. This function randomly rearranges the elements in the array. At the same time, we can use the array_slice() function to obtain new array slices, thereby achieving random selection with controllable probability.

The following is a simple code example:

<?php
$array = array("A", "B", "C", "D", "E");
shuffle($array);
$chance = 30; //生成30%的事件
if (in_array("A", array_slice($array, 0, count($array) * $chance / 100))) {
    // 某些操作
}
?>

In the above code, the shuffle() function will randomly reorder the elements in the $array array. By adjusting the value of $chance, we can easily control the probability of an event occurring. At the same time, the array_slice() function can be used to obtain a new array fragment of a specified length, thereby achieving random selection with controllable probability.

3. Messenne rotation algorithm

The Mersenne rotation algorithm is an efficient random number generation algorithm that can generate high-quality pseudo-random number sequences. The algorithm consists of a state vector that is continuously updated through some transformations to generate random numbers.

In PHP, we can use the Mersenne Twister algorithm library to implement the Mersenne Twister algorithm. The algorithm library includes two random number generation functions: mt_rand() and mt_srand(). Among them, the mt_rand() function is used to generate random numbers, and the mt_srand() function is used to set the random number seed.

The following is a simple code example:

<?php
mt_srand(time());
$chance = 30; //生成30%的事件
if (mt_rand(1, 100) <= $chance) {
    // 某些操作
}
?>

In the above code, mt_rand(1, 100) will generate a random number between 1 and 100. If the random number is less than or equal to 30, some operation will be performed. By adjusting the value of $chance, we can easily control the probability of an event occurring.

Summary

The controllable probability algorithm is a commonly used programming method that can control the probability of random events when necessary. In PHP, we can use a variety of algorithms to achieve random number generation with controllable probability. We can choose the appropriate algorithm according to specific needs to achieve our goals.

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