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Date: Fri, 2 Apr 2021 22:56:22 +0100
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To: Go Kudo <zeriyoshi@gmail.com>
Cc: Levi Morrison <levi.morrison@datadoghq.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [VOTE] Object scoped RNG implementation
From: tekiela246@gmail.com (Kamil Tekiela)

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Hi Go Kudo,

First, let me say that I believe we need such implementation in PHP and I
would like to see object scoped RNG as part of the standard. However, I
have voted no for a number of reasons. Let me list them from the
perspective of a noob PHP user.

- I really do not understand why we are introducing new functions. Can't
the classes implement the necessary methods to get integers, doubles, and
string of bytes? As a new user I would be completely overwhelmed by all
these functions: rand(), mt_rand(), rng_int(), rng_next(), rng_next64().
Which one should I use? What is the difference between rng_next()
and rng_next64?
- As soon as I left the RFC page I forgot what the new classes were called.
I still can't tell from memory what's their name. I understand what they
mean, but they are definitely not friendly names.
- What's the difference between MT19937 and XorShift128Plus? They are
different algorithms but which one should I pick? I tested the
implementation locally and I see no difference in performance.
- I am not a fan of adding a new optional parameter to shuffle() and
friends. I'd prefer to have a method in the class that I can pass an array
to.
- What is the default seed? Do I have to provide a seed each time? Why
can't the seed be done automatically?
- Signed? Unsigned? As far as I know, PHP doesn't have unsigned integers.
What's the real-life purpose of this flag?
- I don't see any use in supporting userland implementations. Why can't
they create separate libraries?  I don't know about performance, but if
someone wants to have custom RNG then I don't think they worry about
performance.
- When using the functions the performance was 50% worse than when calling
->next() directly. Is this right or is the implementation going to be
optimized further? The fastest way to get a random number seems to be
mt_rand() based on my tests.

I would rather like to see a single class called RNG/Random that implements
RNG/RandomInterface. The constructor of the class would take 2 arguments.
The first is the algorithm with a default either MT or XORShift. The second
is an optional seed. If no seed is provided then the seed is generated
automatically like in mt_srand(). The class would then implement methods
like: nextInt(), nextDouble(), nextBytes(), arrayShuffle(),
stringShuffle(), randomArrayKeys(). I would keep the standard functions as
they are. Let them use MT by default. We could even deprecate them in
future if this takes off.

This would make it painfully obvious what the class does and how to use it.
No more procedural code. I would also make the class final so that you
can't inherit from it, but that is highly opinion-based.
Now that I have written this, I read previous conversations and it looks to
me like what I would like is what you had previously.

I'm sorry if I complain too much, but I would like to see something like
this implemented, just not like you are proposing right now. It is too
messy for me and I know I wouldn't like it if I had to use it.

Regards,
Kamil

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