"""
These functions match what the spec of hnswlib is.
"""
from typing import Union, cast
import numpy as np
from numpy.typing import NDArray
Vector = NDArray[Union[np.int32, np.float32, np.int16, np.float16]]
def l2(x: Vector, y: Vector) -> float:
return (np.linalg.norm(x - y) ** 2).item()
def cosine(x: Vector, y: Vector) -> float:
# This epsilon is used to prevent division by zero, and the value is the same
# https://github.com/nmslib/hnswlib/blob/359b2ba87358224963986f709e593d799064ace6/python_bindings/bindings.cpp#L238
# We need to adapt the epsilon to the precision of the input
NORM_EPS = 1e-30
if x.dtype == np.float16 or y.dtype == np.float16:
NORM_EPS = 1e-7
return cast(
float,
(
1.0 - np.dot(x, y) / ((np.linalg.norm(x) * np.linalg.norm(y)) + NORM_EPS)
).item(),
)
def ip(x: Vector, y: Vector) -> float:
return cast(float, (1.0 - np.dot(x, y)).item())