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42 lines
1.4 KiB
Python
42 lines
1.4 KiB
Python
"""Utility functions for working with vectors and vectorstores."""
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from typing import List
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import numpy as np
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from langchain.math_utils import cosine_similarity
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def maximal_marginal_relevance(
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query_embedding: np.ndarray,
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embedding_list: list,
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lambda_mult: float = 0.5,
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k: int = 4,
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) -> List[int]:
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"""Calculate maximal marginal relevance."""
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if min(k, len(embedding_list)) <= 0:
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return []
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if query_embedding.ndim == 1:
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query_embedding = np.expand_dims(query_embedding, axis=0)
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similarity_to_query = cosine_similarity(query_embedding, embedding_list)[0]
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most_similar = int(np.argmax(similarity_to_query))
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idxs = [most_similar]
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selected = np.array([embedding_list[most_similar]])
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while len(idxs) < min(k, len(embedding_list)):
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best_score = -np.inf
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idx_to_add = -1
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similarity_to_selected = cosine_similarity(embedding_list, selected)
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for i, query_score in enumerate(similarity_to_query):
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if i in idxs:
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continue
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redundant_score = max(similarity_to_selected[i])
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equation_score = (
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lambda_mult * query_score - (1 - lambda_mult) * redundant_score
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)
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if equation_score > best_score:
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best_score = equation_score
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idx_to_add = i
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idxs.append(idx_to_add)
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selected = np.append(selected, [embedding_list[idx_to_add]], axis=0)
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return idxs
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