#13 Add numeric distance calculator

Author: pockerman

src/utils/numeric_distance_calculator.py

@@ -0,0 +1,56 @@
+"""
+Various methods to calculate distance between numeric vectors
+"""
+import numpy as np
+from typing import TypeVar
+
+from src.utils.numeric_distance_type import NumericDistanceType
+from src.exceptions.exceptions import IncompatibleVectorSizesException, InvalidParamValue
+
+Vector = TypeVar("Vector")
+
+
+class NumericDistanceCalculator(object):
+
+    def __init__(self, dist_type: NumericDistanceType) -> None:
+        self.dist_type = dist_type
+
+    def calculate(self, state1: Vector, state2: Vector) -> float:
+        return _numeric_distance_calculator(state1=state1, state2=state2, dist_type=self.dist_type)
+
+
+def _numeric_distance_calculator(state1: Vector, state2: Vector, dist_type: NumericDistanceType) -> float:
+
+    if len(state1) != len(state2):
+        raise IncompatibleVectorSizesException(size1=len(state1), size2=len(state2))
+
+    if dist_type == NumericDistanceType.L1:
+        return _l1_state_leakage(state1=state1, state2=state2)
+    elif dist_type == NumericDistanceType.L2:
+        return _l1_state_leakage(state1=state1, state2=state2)
+    elif dist_type == NumericDistanceType.L2_NORMALIZED:
+        return _normalized_l2_distance(state1=state1, state2=state2)
+
+    raise InvalidParamValue(param_name="dist_type", param_value=dist_type.name)
+
+
+def _normalized_l2_distance(state1: Vector, state2: Vector) -> float:
+    """
+    Returns the normalized L2 norm between the two vectors
+    :param state1:
+    :param state2:
+    :return:
+    """
+
+    size = len(state1)
+    dist = 0.0
+    for item1, item2 in zip(state1, state2):
+        dist += ((item1 - item2)**2) / size
+
+    return np.sqrt(dist)
+
+def _l2_state_leakage(state1: Vector, state2: Vector) -> float:
+    return np.linalg.norm(state1 - state2, ord=None)
+
+def _l1_state_leakage(state1: Vector, state2: Vector) -> float:
+    return np.linalg.norm(state1 - state2, ord=1)