PRNGs for GameMaker

Quick links: blog post · documentation · source code
Supported versions: GM2022+, GM LTS
Supported platforms: all
See also: more GameMaker things!

This is a set of custom pseudorandom number generators for GameMaker!

You can use these to:

• Have separate random number generators for different parts of the game.
• Save/load generator's state (for example, to prevent "save scumming", or for networking)
• Have more control over PRNG in general

See the "uses" section in the post for detailed examples!

Included generators

• MINSTD
  This appears as minstd_rand in C++.
  Quick and simple.
• A random_r style generator (called Rand0 for convenience)
  This is an LCG with mod=2³¹, mult=1103515245, inc=12345.
  Also quick and simple.
• Xorshift (64-bit)
  The GML version of this generator is slower than above in VM builds, but much faster in YYC builds!
• Well Equidistributed Long-period Linear (512-bit)
  This is a replica of what GameMaker itself uses for its random functions!
  The GML version is slightly slower than other generators.

Each generator has several variants to choose from:

• GML: Constructor-based (r = gen.float(100))
• GML: Array-based (r = minstd_float(gen, 100))
• GML: Global (r = minstd_float(100))
• C++ DLL edition (Windows-only)

See the "tests" section in the post for performance comparisons between different generators and their implementations! You might be surprised.

Package contents

• GML scripts (one per variant per generator, self-contained)
• C++ DLL extension (optional)
  See notes on mixing it with scripts
• Test project with benchmarks and unit tests.
• Offline documentation