rfc:rng_extension

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rfc:rng_extension [2021/09/03 14:28] – zeriyoshirfc:rng_extension [2022/02/14 10:56] – update github pr uri zeriyoshi
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-====== PHP RFC: Random Extension 3.0 ====== +====== PHP RFC: Random Extension 4.0 ====== 
-  * Version: 3.0 +  * Version: 4.0 
-  * Date: 2021-09-02 +  * Date: 2022-02-14 
-  * Author: Go Kudo <zeriyoshi@gmail.com>+  * Author: Go Kudo <zeriyoshi@gmail.com> <g-kudo@colopl.co.jp>
   * Status: Under Discussion   * Status: Under Discussion
-  * Implementation: https://github.com/php/php-src/pull/7453+  * Implementation: https://github.com/php/php-src/pull/8094
   * First Published at: http://wiki.php.net/rfc/object_scope_prng   * First Published at: http://wiki.php.net/rfc/object_scope_prng
  
 ===== Introduction ===== ===== Introduction =====
  
-Currently, PHP's random number implementation suffers from several problems.+PHP implements several useful RNGs. However, they are currently only available in the global scope.
  
-The first is that there are many different implementations. Historically, the random number implementations have been separated into lcg.c, rand.c, mt_rand.c random.c respectively, and the header file dependencies are complex.+Mersenne Twister, PHP's default RNG, provides a function mt_srand() to initialize with a user-specified seed value, but the scope is global, which may cause unintended user behavior.
  
-Second, the pseudo-random number generator makes use of global state. If a random number is consumed at an unexpected time, the reproducibility of the result may be lost. Look at the following example.+When a user executes mt_srand(), one would expect it to only affect result of mt_rand(), however, the following functions implicitly affect the result of mt_rand()
  
-<code php> +  * shuffle() 
-echo foo(1234, function (): void {}) . PHP_EOL; // Result: 1480009472 +  * str_shuffle() 
-echo foo(1234, function (): void { mt_rand(); }) . PHP_EOL; // Result: 1747253290+  * array_rand()
  
-function foo(int $seed, callable $bar): int { +For example, in the following code, the result of the second mt_rand() is not reproducible. This is because shuffle() uses a MT RNG internally, which changes the state.
-    mt_srand($seed); +
-    $result = mt_rand(); +
-    $bar(); +
-    $result += mt_rand(); +
-    return $result; +
-} +
-</code> +
- +
-Reproducibility of random numbers can easily be lost if additional code is added later. +
- +
-In addition, the fiber extension was introduced in PHP 8.1. This makes it more difficult to keep track of the execution order. However, this problem has existed since the introduced of Generator. +
- +
-There is also the problem of functions that implicitly use the state stored in PHP's global state. shuffle(), str_shuffle(), and array_rand() functions implicitly advance the state of a random number. This means that the following code is not reproducible, but it is difficult for the user to notice this.+
  
 <code php> <code php>
 mt_srand(1234); mt_srand(1234);
-echo mt_rand() . PHP_EOL; // Result: 411284887+$next = mt_rand();
  
 mt_srand(1234); mt_srand(1234);
-str_shuffle('foobar'); +$arr = range(0, 9); 
-echo mt_rand() . PHP_EOL; // Result: 1314500282+shuffle($arr); 
 +$next2 = mt_rand(); 
 + 
 +die("next: ${next}, next2: ${next2}"); // next: 411284887, next2: 1848274264
 </code> </code>
  
-===== Proposal =====+These behaviors were unintuitive and often led to unintended execution results, but were not that problematic for general web application use.
  
-Clean up the implementation, separate out the random number related functions as Random extension, and add an object scoped API.+However, in more complex and repeatable applications (such as games), this can be a problem.
  
-All of the following functions will be moved to the newly created Random extension.+There is also the issue of state management difficulties with Fiber, which was added in PHP 8.1. Nikita had this to say:
  
-  * lcg_value() +https://externals.io/message/115918#115959
-  * srand() +
-  * rand() +
-  * mt_srand() +
-  * mt_rand() +
-  * random_int() +
-  * random_bytes()+
  
-At the same time, the following internal APIs will also be relocated. If you want to use them, you can simply include ext/random/random.h.+In addition, the Mersenne Twister, can only generate 32-bit values. 
 +In recent years, many of the environments where PHP runs have been migrating to 64-bit platforms. 
 +In order to generate more secure values, an RNG that can generate 64-bit wide values should be provided by the language.
  
-  * php_random_int_throw() +===== Proposal =====
-  * php_random_int_silent() +
-  * php_combined_lcg() +
-  * php_mt_srand() +
-  * php_mt_rand() +
-  * php_mt_rand_range() +
-  * php_mt_rand_common() +
-  * php_srand() +
-  * php_rand() +
-  * php_random_bytes() +
-  * php_random_int()+
  
-The following PHP constants will now be provided by the Random extension+Implement the XorShift128Plus algorithm for generating new 64-bit wide random numbers, along with a random extension that includes an object scope RNG, and bundle it with PHP. 
 +XorShift128Plus is a fast, high-quality RNG that is proven in major web browsers.  
 +Many of the major hardware architectures are now 64-bit, so it makes sense to use this RNG.
  
-  * MT_RAND_MT19937 +In addition to the new algorithm, the following classes will be added to fix the global scope issue.
-  * MT_RAND_PHP+
  
-To solve the scope problem, the following classes will be added+  * class Random\NumberGenerator\XorShift128Plus 
 +  * class Random\NumberGenerator\MersenneTwister 
 +  * class Random\NumberGenerator\CombinedLCG 
 +  * class Random\NumberGenerator\Secure (aka php_random_bytes())
  
-  * Random class +These classes will hold independent RNG state and will not affect the global scope.
-  * Random\NumberGenrator abstract class +
-  * Random\NumberGenerator\XorShift128Plus class +
-  * Random\NumberGenerator\MT19937 class +
-  * Random\NumberGenerator\Secure class+
  
-The Random class is a utility class that provides functionality using random numbers. It provides the following methods, but does not provide an alternative to array_rand because it is too complex.+An interface Random\NumberGenerator is also added and are implmeneted by the classes above.  
 +This interface has only a single generate() method which makes it possible to switch between RNG implementations depending on the situation, 
 +allowing alternative implementations to be done by PHP in userland. This is useful, for example, for running tests.
  
-  * getInt() +RNGs other than XorShift128Plus are based on the RNGs currently implemented in PHP.
-  * getBytes() +
-  * shuffleArray() +
-  * shuffleString()+
  
-This class can be used in the following way.+The Random\Randomizer class will be added to manipulate data using these RNGs. 
  
-<code php> +This class provides the following methods:
-// functions +
-mt_srand(1234); +
-mt_rand(); // generate random number +
-mt_rand(1, 10); // generate random number in range +
-str_shuffle("foobar"); // shuffle string +
-$arr = range(1, 10); +
-shuffle($arr); // shuffle array items (pass by reference)+
  
-// object +  * __constructor(\Random\NumberGenerator $generator = null) [defaults to XorShift128Plus if null] 
-$mt = new Random\NumberGenerator\MT19937(1234); +  * getInt(int $min, int $max): int [replacement for mt_rand() / rand()] 
-$mt->generate(); // generate random number  +  * getBytes(int $length): string [replacement for random_bytes()] 
-$random = new Random($mt); +  * shuffleArray(array $array): array [replacement for shuffle()] 
-$random->getInt(1, 10); // generate random number in range +  * shuffleString(string $string): string [replacement for str_shuffle()]
-$random->shuffleString("foobar"); // shuffle string +
-$random->shuffleArray(range(1, 10)); // shuffle array items (pass by value) +
-</code>+
  
-The Random class accepts an instance that inherits from Random\NumberGenerator as a constructor argument.+Method equivalent to array_rand() was not implemented at this time because the implementation is complex and can be easily implemented in userland if necessary.
  
-This class is final and cannot be cloned, but it can be serialized. +Examples of these uses are as follows:
-This is to prevent $rng from being copied by reference to a property and causing unintended behavior. +
- +
-The serializability depends on the serializability of the contained $rng.+
  
 <code php> <code php>
-final class Random +// Use different RNGs for different environments. 
-{ +$rng = $is_production 
-    private Random\NumberGenerator $randomNumberGenerator; +    ? new Random\NumberGenerator\Secure() 
- +    : new Random\NumberGenerator\XorShift128Plus(1234);
-    public function __construct(?Random\NumberGenerator $randomNumberGenerator = null) {} +
-    public function getNumberGenerator(): Random\NumberGenerator {} +
-    public function getInt(int $min, int $max): int {} +
-    public function getBytes(int $length): string {} +
-    public function shuffleArray(array $array): array {} +
-    public function shuffleString(string $string): string {}+
  
-    public function __serialize(): array {} +$randomizer = new Random\Randomizer($rng); 
-    public function __unserialize(array $data): void {} +$randomizer->shuffleString('foobar');
-}+
 </code> </code>
- 
-The Random\NumberGenerator abstract class has a single abstract method called generate().  
  
 <code php> <code php>
-namespace Random;+// Safely migrate the existing mt_rand() state.
  
-abstract class NumberGenerator +// before 
-{ +mt_srand(1234, MT_RAND_PHP); 
-        abstract public function generate(): int {} +foobar(); 
-} +$result = str_shuffle('foobar');
-</code>+
  
-By defining a class that extends Random\NumberGenerator, the user can use their own random number generator. With the introduction of JIT in PHP 8.0, this can generate random numbers at a realistic speed. +// after 
- +$randomizer = new Random\Randomizer(new Random\NumberGenerator\MersenneTwister(1234, MT_RAND_PHP)); 
-<code php> +foobar(); 
-class UserDefinedRNG extends Random\NumberGenerator +$result = $randomizer->stringShuffle('foobar');
-{ +
-    protected int $current = 0; +
- +
-    public function generate(): int +
-    { +
-        return ++$this->current; +
-    } +
-} +
- +
-function foobar(Random\NumberGenerator $numberGenerator): void { +
-    for ($i = 0; $i < 9; $i++) { +
-        echo $numberGenerator->generate(); +
-    } +
-} +
- +
-foobar(new UserDefinedRNG()); // Results: 123456789+
 </code> </code>
  
-It is also useful when you want to use a random number sequence with a fixed result, such as in testing.+As a side effect of this RFC, the following PHP functions have been moved to the new ext/random extension
  
-The Random class creates and uses an instance of the default random number generator, Random\NumberGenerator\XorShift128Plus, if the constructor argument is omitted.+This is because ext/standard/random.c reserves the name RANDOM and cannot be used by the extension. 
 +In addition, all RNG-related implementations will be moved to the new random extension in order to standardize the RNG implementation.
  
-XorShift128Plus is an efficient, high-quality algorithm used in modern browsers and other applications. This algorithm is capable of generating a wider range of random numbers in a 64-bit environment. In a 32-bit environment, the range beyond zend_long will simply be truncated. This indicates incompatibility between environments, but is acceptable for real-world use.+  * lcg_value() 
 +  * srand() 
 +  * rand() 
 +  * mt_srand() 
 +  * mt_rand() 
 +  * random_int() 
 +  * random_bytes()
  
-The Random\NumberGenerator\MT19937 class, which implements the MT19937 Mersenne twister, is also provided for backward compatibility or when a higher period is required. However, a 1-bit right shift is required to obtain exactly the same result as mt_rand(), as shown below. This is due to historical reasons.+The following internal APIs will also be moved to the ext/random extension:
  
-<code php> +  * php_random_int_throw() 
-$seed = 1234;+  * php_random_int_silent() 
 +  * php_combined_lcg() 
 +  * php_mt_srand() 
 +  * php_mt_rand() 
 +  * php_mt_rand_range() 
 +  * php_mt_rand_common() 
 +  * php_srand() 
 +  * php_rand() 
 +  * php_random_bytes() 
 +  * php_random_int()
  
-$mt = new Random\NumberGenerator\MT19937($seed); +All of these features are available from the extension by simply including a single ext/random/php_random.h
-mt_srand($seed); +
-var_dump(mt_rand() === ($mt->generate() >> 1)); // true +
-</code>+
  
-The following NumberGenerator class supports serialization. Secure is not serializable because it uses random_bytes internally and has no state.+The following header files are left in for extension compatibility. The contents all include ext/random/php_random.h.
  
-  * Random\NumberGenerator\XorShift128Plus +  * ext/standard/php_lcg.h 
-  * Random\NumberGenerator\MT19937 +  * ext/standard/php_rand.h 
-  * Random\NumberGenerator extends user-defined classes. +  * ext/standard/php_mt_rand.h 
- +  * ext/standard/php_random.h
-Also, a new internal API will be implemented. +
- +
-  * php_random_ng_next() +
-  * php_random_ng_range() +
-  * php_random_ng_array_data_shuffle() +
-  * php_random_ng_string_shuffle() +
- +
-A Stub showing these implementations can be found on the Pull-Request. It's probably easier to understand if you look at it. +
- +
-  * [[https://github.com/php/php-src/blob/7a4ef6ccfbf4a2cd48a4f261f2911ebb7b057d46/ext/random/random.stub.php|random.stub.php]]+
  
 ===== Future Scope ===== ===== Future Scope =====
  
-This proposal is just a first step to improve the situation of PHP's random number implementation.+These are not within the scope of this RFC, but are worth considering in the future:
  
-If this proposal is approved, I will then propose the following changes +  * Remove old header files for compatibility (php_lcg.h, php_rand.h, php_mt_rand.h, php_random.h) 
- +  * Deprecate lcg_value(), mt_srand(), srand()
-  * Replace the state of the existing implementation with php_random_ng. +
-  * Changes random source to php_random_int() a shuffle(), str_shuffle(), and array_rand() . +
-  * Deprecate srand() and mt_srand() (step by step)+
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
  
-The code that includes the following header file needs to be changed to ext/random/random.h +The following names have been reserved and will no longer be available
- +
-  * ext/standard/lcg.h +
-  * ext/standard/rand.h +
-  * ext/standard/mt_rand.h +
-  * ext/standard/random.h +
- +
-The following class names have been reserved and will no longer be available+
  
   * "Random"   * "Random"
   * "Random\NumberGenerator"   * "Random\NumberGenerator"
   * "Random\NumberGenerator\XorShift128Plus"   * "Random\NumberGenerator\XorShift128Plus"
-  * "Random\NumberGenerator\MT19937"+  * "Random\NumberGenerator\MersenneTwister" 
 +  * "Random\NumberGenerator\CombinedLCG"
   * "Random\NumberGenerator\Secure"   * "Random\NumberGenerator\Secure"
  
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 ==== To Existing Extensions ==== ==== To Existing Extensions ====
-none+In the future, it may be necessary to change the included header files to point to ext/random/php_random.h. However, compatibility will be maintained for now.
  
 ==== To Opcache ==== ==== To Opcache ====
Line 251: Line 181:
  
 ===== Vote ===== ===== Vote =====
-Voting opens 2021-MM-DD and 2021-MM-DD at 00:00:00 EDT. 2/3 required to accept.+Voting opens 2022-MM-DD and 2021-MM-DD at 00:00:00 EDT. 2/3 required to accept.
  
-<doodle title="Add Random class" auth="zeriyoshi" voteType="single" closed="true"> +<doodle title="Add Random extension" auth="zeriyoshi" voteType="single" closed="true"> 
    * Yes    * Yes
    * No    * No
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 ===== Patches and Tests ===== ===== Patches and Tests =====
-  * https://github.com/php/php-src/pull/7453+  * https://github.com/php/php-src/pull/8094
rfc/rng_extension.txt · Last modified: 2022/08/01 16:52 by timwolla

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