langchain/math_utils.py/cosine_similarity_top_k
def cosine_similarity_top_k(
    X: Matrix,
    Y: Matrix,
    top_k: Optional[int] = 5,
    score_threshold: Optional[float] = None,
) -> Tuple[List[Tuple[int, int]], List[float]]:
    """Row-wise cosine similarity with optional top-k and score threshold filtering.

    Args:
        X: Matrix.
        Y: Matrix, same width as X.
        top_k: Max number of results to return.
        score_threshold: Minimum cosine similarity of results.

    Returns:
        Tuple of two lists. First contains two-tuples of indices (X_idx, Y_idx),
            second contains corresponding cosine similarities.
    """
    if len(X) == 0 or len(Y) == 0:
        return [], []
    score_array = cosine_similarity(X, Y)
    sorted_idxs = score_array.flatten().argsort()[::-1]
    top_k = top_k or len(sorted_idxs)
    top_idxs = sorted_idxs[:top_k]
    score_threshold = score_threshold or -1.0
    top_idxs = top_idxs[score_array.flatten()[top_idxs] > score_threshold]
    ret_idxs = [(x // score_array.shape[1], x % score_array.shape[1]) for x in top_idxs]
    scores = score_array.flatten()[top_idxs].tolist()
    return ret_idxs, scores