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mt_srand

(PHP 4, PHP 5, PHP 7, PHP 8)

mt_srand — Seeds the Mersenne Twister Random Number Generator

Açıklama

mt_srand(?int $seed = null, int $mode = MT_RAND_MT19937): void

Seeds the random number generator with seed or with a random value if no seed is given.

Bilginize: Otomatik olarak yapıldığından srand() veya mt_srand() işleviyle rasgele sayı üretecini tohumlamaya ihtiyaç yoktur.

Dikkat

Because the Mt19937 (“Mersenne Twister”) engine accepts only a single 32 bit integer as the seed, the number of possible random sequences is limited to just 232 (i.e. 4,294,967,296), despite Mt19937’s huge period of 219937-1.

When relying on either implicit or explicit random seeding, duplications will appear much earlier. Duplicated seeds are expected with 50% probability after less than 80,000 randomly generated seeds according to the birthday problem. A 10% probability of a duplicated seed happens after randomly generating roughly 30,000 seeds.

This makes Mt19937 unsuitable for applications where duplicated sequences must not happen with more than a negligible probability. If reproducible seeding is required, both the Random\Engine\Xoshiro256StarStar and Random\Engine\PcgOneseq128XslRr64 engines support much larger seeds that are unlikely to collide randomly. If reproducibility is not required, the Random\Engine\Secure engine provides cryptographically secure randomness.

Bağımsız Değişkenler

seed

Fills the state with values generated with a linear congruential generator that was seeded with seed interpreted as an unsigned 32 bit integer.

If seed is omitted or null, a random unsigned 32-bit integer will be used.

mode

Use one of the following constants to specify the implementation of the algorithm to use.

  • MT_RAND_MT19937: The correct Mt19937 implementation, available as of PHP 7.1.0.
  • MT_RAND_PHP Uses an incorrect Mersenne Twister implementation which was used as the default up till PHP 7.1.0. This mode is available for backward compatibility.

Uyarı

Bu özelliğin kullanımı PHP 8.3.0 itibariyle ÖNERİLMEMEKTEDİR. Bu özelliğe kesinlikle güvenilmemelidir.

Dönen Değerler

Hiçbir değer dönmez.

Sürüm Bilgisi

Sürüm: Açıklama
8.3.0 seed is now nullable.
7.1.0 srand() has been made an alias of mt_srand().
7.1.0 mt_rand() has been updated to use the fixed, correct, version of the Mersenne Twister algorithm. To fall back to the old behaviour, use mt_srand() with MT_RAND_PHP as the second parameter.

Ayrıca Bakınız