rfc:rng_extension

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
Next revisionBoth sides next revision
rfc:rng_extension [2021/09/03 14:02] – add more example zeriyoshirfc:rng_extension [2022/02/14 14:28] – fix stringShuffle -> shuffleString zeriyoshi
Line 1: Line 1:
-====== 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->shuffleString('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. +
-  * Replace random_bytes() with random_bytes() for random numbers used in 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"
  
Line 236: Line 166:
  
 ==== 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
Line 259: Line 189:
  
 ===== 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

Page Tools