Pseudorandom number generation in Pokémon

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Revision as of 20:14, 11 December 2013 by Takoto (talk | contribs) (RNG Abuse: The word "Generation" is written twice.)
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A pseudorandom number generator is an electronic device or software's attempt at creating a random number. Just as rolling a dice is not 'random' (being determined by factors such as force and angle of the throw, as well as friction), computers cannot be truly 'random'. In order to generate 'random' events in games and other forms of software, they must get as close to looking it as they can. There are limitless ways of accomplishing this. The degree of apparent randomness depends on the ability to predict the next result of the algorithm.


First, the generator must have a seed, a number to start with. This number is usually a date and time referring to the first time that the algorithm is called during the usage of the device or the software's active session. Seeds are also occasionally derived from user input, as it is highly improbable to do the exact same thing more than once, making it appear 'random'.

This number is put through a complex algorithm, and the result is formatted according to the needed context. The raw result then becomes the seed for any subsequent uses of the random generator. Therefore, the nature of the generator is a recursive algorithm.

In the Pokémon games

Linear Congruential random number generator (LCRNG)

In Generation III and Generation IV, the games use a 32 bit LCRNG.

Let Seed be a number between 0 and 0xFFFFFFFF or the Result of a previous call to the equation.

Result = [(0x41C64E6D * Seed) + 0x6073]

This algorithm is used for the following:

In Generation V, the games instead use a 64 bit LCRNG as follows:

Result = [(0x5D588B656C078965 * Seed) + 0x0000000000269EC3]

Alternative pseudorandom number generator (ARNG)

The Generation IV games also use a different algorithm to alternate, reroll, or modify a previously randomly generated value. The algorithm works in the same nature; however, the equation changes to:

Result = [(0x6C078965 * Seed) + 0×1]

This algorithm is used for the following:

Mersenne Twister (MTRNG)

Found in Generation IV and later, the Mersenne Twister is another type of random number generator that produces 624 random numbers at once. These random numbers are then stored and used when needed. When all 624 numbers are used, another set is generated.

This algorithm is used for the following:

RNG Abuse

RNG abuse, also referred to as RNG manipulation, is a procedure that manipulates the pseudorandom number generators in the main series games to obtain a desired Pokémon. It is commonly used to obtain Shiny Pokémon, Pokémon with high individual values, Pokémon with a specific set of individual values that yield a particular Hidden Power output (regarding Type and/or move Power), or Pokémon with certain Natures.

In games where the initial seed (on startup) is predictable, the subsequent "random" numbers are predictable as well. Pokémon Emerald's initial seed is always 0. The Generation IV games use the Nintendo DS's date, time, and delay between starting the game and pressing "Continue" to generate the initial seed. V games use the Nintendo DS's date, time, keys currently pressed, and other entropy data to create a seed moments before the Nintendo logo appears.

The random number generator is used to determine a Pokémon's personality value and individual values when it is encountered or received. By searching for initial seeds that satisfy the characteristics required, the player can then hit the target seed and advance 'frames' to receive their target characteristics. There are several methods used to influence a Pokémon's characteristics — for instance, a bred Pokémon and a stationary wild Pokémon's characteristics are generated through different methods.

In Generation III and Generation IV, there are some limitations. As a player's Trainer ID and Secret ID numbers determine a Pokémon's shininess, Shiny Pokémon generated through certain methods can only have certain individual values. Due to Wonder Card gifts using a timer register to create personality values, it is not possible to manipulate a gift's Nature. In Generation V, this is no longer the case as the individual values and personality values are determined from two different RNGs.

In the Pokémon fandom, RNG abuse is slightly controversial. Proponents note that RNG abuse does not require a third-party device and that the Pokémon obtained through RNG abuse can be obtained through normal gameplay. In addition, Pokémon obtained through RNG abuse have been used at the Video Game Championships, an official tournament. However, some players believe that RNG abuse is cheating, as the action of picking a Pokémon's characteristics is similar to using a cheating device.

External links

Project Games logo.png This game mechanic article is part of Project Games, a Bulbapedia project that aims to write comprehensive articles on the Pokémon games.