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mruby-random: update readme to reflect pcg algorithm

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updates algorithm section to document the change from xoshiro128++
to PCG-XSH-RR. highlights key benefits including 50% memory reduction,
platform-adaptive optimization, and excellent statistical quality.

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2025-10-15 19:00:52 +09:00
parent f1bab01b4c
commit 413446657c
1 changed files with 11 additions and 2 deletions
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mrbgems/mruby-random/README.md
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@@ -254,9 +254,18 @@ The `sample` method chooses one or more random elements from the array.
## Algorithm
The `mruby-random` mrbgem primarily utilizes the **xoshiro128++ 1.0** algorithm for pseudo-random number generation.
The `mruby-random` mrbgem uses the **PCG-XSH-RR** (Permuted Congruential Generator - XorShift High, Random Rotate) algorithm for pseudo-random number generation.
In certain 32-bit configurations (specifically when `MRB_INT32` is defined and `MRB_64BIT` is not), a different algorithm, **XORSHIFT96**, might be employed.
### Key Features
- **Compact State**: Uses only 64 bits of state (compared to 128 bits in the previous xoshiro128++ implementation), reducing memory footprint by 50%
- **Excellent Statistical Quality**: Passes rigorous statistical test suites (TestU01, PractRand)
- **Platform-Optimized**: Automatically adapts to platform characteristics for optimal performance
- On **32-bit platforms** (`MRB_32BIT`): Uses an optimized 32-bit multiplier that requires only 2 multiply operations instead of 3
- On **64-bit platforms**: Uses the standard 64-bit multiplier for maximum statistical quality
- **Fast Performance**: Competitive speed with modern PRNG algorithms while maintaining smaller memory footprint
The PCG family of algorithms was developed by Melissa O'Neill and is widely used in production systems. For more details, see <https://www.pcg-random.org/>.
## License