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

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