# splitmix

Pure Haskell implementation of SplitMix pseudo-random number generator.

## dieharder

Dieharder is a random
number generator (rng) testing suite. It is intended to test generators, not
files of possibly random numbers as the latter is a fallacious view of what it
means to be random. Is the number 7 random? If it is generated by a random
process, it might be. If it is made up to serve the purpose of some argument
(like this one) it is not. Perfect random number generators produce “unlikely”
sequences of random numbers – at exactly the right average rate. Testing a rng
is therefore quite subtle.

```
time dieharder-input splitmix | dieharder -a -g 200
```

The test-suite takes around half-an-hour to complete.
All tests are PASSED (occasionally WEAK).

In comparison, built-in Marsenne Twister
test takes around 15min.

```
time dieharder-input -a
```

## benchmarks

```
benchmarking list/random
time 96.77 μs (96.28 μs .. 97.35 μs)
1.000 R² (1.000 R² .. 1.000 R²)
mean 96.77 μs (96.35 μs .. 97.63 μs)
std dev 2.001 μs (1.028 μs .. 3.796 μs)
variance introduced by outliers: 15% (moderately inflated)
benchmarking list/tf-random
time 60.43 μs (60.12 μs .. 60.79 μs)
1.000 R² (1.000 R² .. 1.000 R²)
mean 60.52 μs (60.26 μs .. 60.91 μs)
std dev 1.120 μs (780.2 ns .. 1.513 μs)
variance introduced by outliers: 14% (moderately inflated)
benchmarking list/splitmix
time 16.38 μs (16.29 μs .. 16.47 μs)
1.000 R² (0.999 R² .. 1.000 R²)
mean 16.34 μs (16.25 μs .. 16.51 μs)
std dev 386.8 ns (201.5 ns .. 669.8 ns)
variance introduced by outliers: 24% (moderately inflated)
benchmarking tree/random
time 115.4 μs (108.6 μs .. 126.0 μs)
0.942 R² (0.910 R² .. 0.977 R²)
mean 116.0 μs (110.3 μs .. 124.2 μs)
std dev 23.47 μs (16.60 μs .. 33.95 μs)
variance introduced by outliers: 95% (severely inflated)
benchmarking tree/tf-random
time 132.4 μs (132.2 μs .. 132.5 μs)
1.000 R² (1.000 R² .. 1.000 R²)
mean 132.5 μs (132.3 μs .. 132.6 μs)
std dev 403.3 ns (323.0 ns .. 516.5 ns)
benchmarking tree/splitmix
time 59.80 μs (59.42 μs .. 60.15 μs)
1.000 R² (0.999 R² .. 1.000 R²)
mean 59.61 μs (59.26 μs .. 60.36 μs)
std dev 1.683 μs (864.5 ns .. 3.206 μs)
variance introduced by outliers: 27% (moderately inflated)
```

Note: the performance can be potentially further improved when GHC gets
SIMD Support.