Re: [RFC] [Under Discussion] Random Extension 4.0

2022年2月15日(火) 22:09 Tim Düsterhus <tim@bastelstu.be>: > Hi > > On 2/15/22 12:48, Go Kudo wrote: > > At first, I updated the RFC to the latest status. > > > > https://wiki.php.net/rfc/rng_extension > > Thank you, the examples are useful. > > > I need some time to think about the current issue. I understand its > > usefulness, but I feel uncomfortable with the fact that the > NumberGenerator > > generates a string. > > Would you feel more comfortable if the interface would be called > \Random\Engine or \Random\Generator (i.e. leaving out the "Number" from > the interface name)? > > Engine is the term used by C++: > > https://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine > Generator is the term used by Java: > > > https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/random/RandomGenerator.html > > ---------- > > With the 'FixedForUnitTest' example you mentioned in the RFC: While for > that specific implementation it appears pretty obvious that increasing > numbers are generated, in practice: > > 1. This will result in inconsistent behavior based on the architecture. > I can't test it due to the lack of the necessary architectures, but I > believe the following to be accurate: > > $g = new FixedForUnitTest(); > > $r = new Randomizer($g); > > // 0100000000000000 in 64 Bit little endian > // 0100000002000000 in 32 Bit little endian > // 0000000000000001 in 64 Bit big endian > var_dump(bin2hex($r->getBytes(8))); > > 2. This analogy completely breaks down for the 'shuffle' functions which > call the generator internally an unspecified number of times: > > $g = new FixedForUnitTest(); > > $r = new Randomizer($g); > > var_dump($r->shuffleString("abcdefghijklmnopqrstuvwxyz")); // > wosqyrupatvxznmlkjihgfedcb > var_dump($r->shuffleString("abcdefghijklmnopqrstuvwxyz")); // > fwrtjndlsyvpzuhxbqomkigeca > > The resulting strings look somewhat ordered, but there is no clear > pattern, despite the underlying generator being completely predictable! > > > I also wonder about the point of changing RNG to XorShift128Plus. There > are > > a number of derived implementations, which RNG do you think is more > > suitable? > > > > I'm not an expert in RNGs, but based off this page: > https://prng.di.unimi.it/ and the linked papers it appears that > xoshiro256** is the overall best choice if memory usage is not a concern. > > Best regards > Tim Düsterhus > Hi Tim. Thanks for the good idea. I changed the NumberGenerator to Engine and changed generate() to return a string as suggested. The main changes since last time are as follows: - The userland implementation can now specify the width of the random number sequence that can be generated - Random\Engine::nextByteSize() has been added - Random\Engine::generate() now returns a string - Random\Randomizer::getInt() now accepts an empty argument (like mt_rand()) At the same time, I have updated the RFC. https://wiki.php.net/rfc/rng_extension I have not yet come to a final conclusion on whether XorShift128Plus should be switched to another RNG. For example, what about implementing XorShift128Plus, but adding Xoshiro256** as well?