import rand import math const ( range_limit = 40 value_count = 1000 seeds = [u32(42), 256] ) const ( sample_size = 1000 stats_epsilon = 0.05 inv_sqrt_12 = 1.0 / math.sqrt(12) ) fn get_n_randoms(n int, r rand.SysRNG) []int { mut ints := []int{cap: n} for _ in 0 .. n { ints << r.int() } return ints } fn test_sys_rng_reproducibility() { // Note that C.srand() sets the seed globally. // So the order of seeding matters. It is recommended // to obtain all necessary data first, then set the // seed for another batch of data. for seed in seeds { seed_data := [seed] r1 := rand.SysRNG{} r2 := rand.SysRNG{} r1.seed(seed_data) ints1 := get_n_randoms(value_count, r1) r2.seed(seed_data) ints2 := get_n_randoms(value_count, r2) assert ints1 == ints2 } } // TODO: use the `in` syntax and remove this function // after generics has been completely implemented fn found(value u64, arr []u64) bool { for item in arr { if value == item { return true } } return false } fn test_sys_rng_variability() { // If this test fails and if it is certainly not the implementation // at fault, try changing the seed values. Repeated values are // improbable but not impossible. for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) mut values := []u64{cap: value_count} for i in 0 .. value_count { value := rng.u64() assert !found(value, values) assert values.len == i values << value } } } fn check_uniformity_u64(rng rand.SysRNG, range u64) { range_f64 := f64(range) expected_mean := range_f64 / 2.0 mut variance := 0.0 for _ in 0 .. sample_size { diff := f64(rng.u64n(range)) - expected_mean variance += diff * diff } variance /= sample_size - 1 sigma := math.sqrt(variance) expected_sigma := range_f64 * inv_sqrt_12 error := (sigma - expected_sigma) / expected_sigma assert math.abs(error) < stats_epsilon } fn test_sys_rng_uniformity_u64() { // This assumes that C.rand() produces uniform results to begin with. // If the failure persists, report an issue on GitHub ranges := [14019545, 80240, 130] for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for range in ranges { check_uniformity_u64(rng, range) } } } fn check_uniformity_f64(rng rand.SysRNG) { expected_mean := 0.5 mut variance := 0.0 for _ in 0 .. sample_size { diff := rng.f64() - expected_mean variance += diff * diff } variance /= sample_size - 1 sigma := math.sqrt(variance) expected_sigma := inv_sqrt_12 error := (sigma - expected_sigma) / expected_sigma assert math.abs(error) < stats_epsilon } fn test_sys_rng_uniformity_f64() { // The f64 version for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) check_uniformity_f64(rng) } } fn test_sys_rng_u32n() { max := 16384 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.u32n(max) assert value >= 0 assert value < max } } } fn test_sys_rng_u64n() { max := u64(379091181005) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.u64n(max) assert value >= 0 assert value < max } } } fn test_sys_rng_u32_in_range() { max := 484468466 min := 316846 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.u32_in_range(min, max) assert value >= min assert value < max } } } fn test_sys_rng_u64_in_range() { max := u64(216468454685163) min := u64(6848646868) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.u64_in_range(min, max) assert value >= min assert value < max } } } fn test_sys_rng_intn() { max := 2525642 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.intn(max) assert value >= 0 assert value < max } } } fn test_sys_rng_i64n() { max := i64(3246727724653636) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.i64n(max) assert value >= 0 assert value < max } } } fn test_sys_rng_int_in_range() { min := -4252 max := 23054962 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.int_in_range(min, max) assert value >= min assert value < max } } } fn test_sys_rng_i64_in_range() { min := i64(-24095) max := i64(324058) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.i64_in_range(min, max) assert value >= min assert value < max } } } fn test_sys_rng_int31() { max_u31 := 0x7FFFFFFF sign_mask := 0x80000000 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.int31() assert value >= 0 assert value <= max_u31 // This statement ensures that the sign bit is zero assert (value & sign_mask) == 0 } } } fn test_sys_rng_int63() { max_u63 := i64(0x7FFFFFFFFFFFFFFF) sign_mask := i64(0x8000000000000000) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.int63() assert value >= 0 assert value <= max_u63 assert (value & sign_mask) == 0 } } } fn test_sys_rng_f32() { for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.f32() assert value >= 0.0 assert value < 1.0 } } } fn test_sys_rng_f64() { for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.f64() assert value >= 0.0 assert value < 1.0 } } } fn test_sys_rng_f32n() { max := f32(357.0) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.f32() assert value >= 0.0 assert value < max } } } fn test_sys_rng_f64n() { max := 1.52e6 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.f64() assert value >= 0.0 assert value < max } } } fn test_sys_rng_f32_in_range() { min := f32(-24.0) max := f32(125.0) for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.f32() assert value >= min assert value < max } } } fn test_sys_rng_f64_in_range() { min := -548.7 max := 5015.2 for seed in seeds { seed_data := [seed] rng := rand.SysRNG{} rng.seed(seed_data) for _ in 0 .. range_limit { value := rng.f64() assert value >= min assert value < max } } }