File size: 1,379 Bytes
2ca80ad | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | from __future__ import annotations
import hashlib
import math
def _u64(seed: bytes, counter: int) -> int:
h = hashlib.blake2b(digest_size=8)
h.update(seed)
h.update(counter.to_bytes(8, "little", signed=False))
return int.from_bytes(h.digest(), "little", signed=False)
def uniform01(seed: bytes, counter: int) -> float:
"""
Deterministic uniform float in (0, 1), derived from (seed, counter).
"""
# Map 64-bit integer to (0, 1) with clamping away from endpoints
x = _u64(seed, counter)
u = (x + 1.0) / (2**64 + 1.0)
# Defensive clamp (should already be in (0, 1))
if u <= 0.0:
return 1.0 / (2**64 + 1.0)
if u >= 1.0:
return 1.0 - (1.0 / (2**64 + 1.0))
return float(u)
def uniform(seed: bytes, counter: int, low: float, high: float) -> float:
return low + (high - low) * uniform01(seed, counter)
def normal(seed: bytes, counter: int, mean: float = 0.0, std: float = 1.0) -> float:
"""
Deterministic normal via Box-Muller transform.
Uses counters (counter, counter+1) internally.
"""
u1 = uniform01(seed, counter)
u2 = uniform01(seed, counter + 1)
r = math.sqrt(-2.0 * math.log(u1))
theta = 2.0 * math.pi * u2
z0 = r * math.cos(theta)
return mean + std * z0
def uint31(seed: bytes, counter: int) -> int:
return int(_u64(seed, counter) & 0x7FFF_FFFF)
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