24 ms·

Initializing the mersenne twister is really hard: https://github.com/PetterS/monolith/blob/master/minimum/core/random.h https://github.com/PetterS/monolith/blob

Initializing the mersenne twister is really hard: https://github.com/PetterS/monolith/blob/master/minimum/core/random.h https://github.com/PetterS/monolith/blob/master/minimum/core... Edit: There are two links in the code with more info.

dearrifling 8y ago
One shouldn't std::move in a return. Returning a local is already automatically an rvalue, however explicitly moving it disables copy elision.
- petters 8y ago
  You are completely right. That should be fixed
netheril96 8y ago
Most other random libraries, in whatever languages, do not even offer the option of this "right" version of initialization. They all just seed with a 32-bit integer. If you are content with those libraries, you should be content with a simple `std::mt19937{std::random_device{}()}`.
- whyever 8y ago
  I don't think this is true for modern languages. Rust seeds the whole state by default: https://docs.rs/rand/0.6.5/rand/ https://docs.rs/rand/0.6.5/rand/ Julia seems to seed 128 bits: https://github.com/JuliaLang/julia/blob/5741c7f53c5ea443bbd73cc5157b83de415c6d1b/stdlib/Random/src/RNGs.jl#L249 https://github.com/JuliaLang/julia/blob/5741c7f53c5ea443bbd7... However, your statement seems to apply to old languages: C# uses only 32 bits and the time for seeding: https://docs.microsoft.com/en-us/dotnet/api/system.random?view=netframework-4.8 https://docs.microsoft.com/en-us/dotnet/api/system.random?vi... Java only supports 48 bit seeds: https://docs.oracle.com/javase/8/docs/api/java/util/Random.html https://docs.oracle.com/javase/8/docs/api/java/util/Random.h...
madisfun 8y ago
Mersenne Twister has a huge state, and if you have to use the MT (you need a very long period), you will probably want to be able to initialize it properly. For the common use case is a linear congruential generator which is initialized with just one integer.
- GoblinSlayer 8y ago
  Huh? You can't possibly need a period 2^19937-1.

dearrifling 8y ago

One shouldn't std::move in a return. Returning a local is already automatically an rvalue, however explicitly moving it disables copy elision.

petters 8y ago
You are completely right. That should be fixed

netheril96 8y ago

Most other random libraries, in whatever languages, do not even offer the option of this "right" version of initialization. They all just seed with a 32-bit integer. If you are content with those libraries, you should be content with a simple `std::mt19937{std::random_device{}()}`.

whyever 8y ago
I don't think this is true for modern languages. Rust seeds the whole state by default: https://docs.rs/rand/0.6.5/rand/ https://docs.rs/rand/0.6.5/rand/ Julia seems to seed 128 bits: https://github.com/JuliaLang/julia/blob/5741c7f53c5ea443bbd73cc5157b83de415c6d1b/stdlib/Random/src/RNGs.jl#L249 https://github.com/JuliaLang/julia/blob/5741c7f53c5ea443bbd7... However, your statement seems to apply to old languages: C# uses only 32 bits and the time for seeding: https://docs.microsoft.com/en-us/dotnet/api/system.random?view=netframework-4.8 https://docs.microsoft.com/en-us/dotnet/api/system.random?vi... Java only supports 48 bit seeds: https://docs.oracle.com/javase/8/docs/api/java/util/Random.html https://docs.oracle.com/javase/8/docs/api/java/util/Random.h...

madisfun 8y ago

Mersenne Twister has a huge state, and if you have to use the MT (you need a very long period), you will probably want to be able to initialize it properly. For the common use case is a linear congruential generator which is initialized with just one integer.

GoblinSlayer 8y ago
Huh? You can't possibly need a period 2^19937-1.