Yukihiro "Matz" Matsumoto b9090b089e random.c: unbiased rand(n), faster bytes, cheaper sample/shuffle ...

- Replace modulo with rejection sampling in rand_i() to remove modulo bias.
  This yields uniform integers in [0, max) and ensures Fisher–Yates
  shuffles are truly uniform.
- Speed up Random#bytes by writing 4 bytes per PRNG call (pack a uint32_t)
  and add a negative-size check (raise ArgumentError).
- Minor shuffle! tweak: hoist RARRAY_PTR/length out of the loop to avoid
  repeated lookups.
- Lower GC pressure in Array#sample(n): collect unique indices in a small
  C buffer, then push array elements directly, avoiding temporary Ruby
  integers.

Behavioral notes:
- rand(n) and methods depending on it now have unbiased distributions.
- Random#bytes(size) now explicitly rejects negative sizes.
- Other semantics remain unchanged.

Co-authored-by: OpenAI Coding Assistant <noreply@openai.com>

2025-08-14 10:53:10 +09:00

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random.c

random.c: unbiased rand(n), faster bytes, cheaper sample/shuffle

2025-08-14 10:53:10 +09:00