GuidesEvaluationString EvaluatorsEmbedding DistanceOn this pageEmbedding DistanceTo measure semantic similarity (or dissimilarity) between a prediction and a reference label string, you could use a vector vector distance metric the two embedded representations using the embedding_distance evaluator.[1]Note: This returns a distance score, meaning that the lower the number, the more similar the prediction is to the reference, according to their embedded representation.Check out the reference docs for the EmbeddingDistanceEvalChain for more info.from langchain.evaluation import load_evaluatorevaluator = load_evaluator("embedding_distance")evaluator.evaluate_strings(prediction="I shall go", reference="I shan't go")    {'score': 0.0966466944859925}evaluator.evaluate_strings(prediction="I shall go", reference="I will go")    {'score': 0.03761174337464557}Select the Distance Metric​By default, the evalutor uses cosine distance. You can choose a different distance metric if you'd like. from langchain.evaluation import EmbeddingDistancelist(EmbeddingDistance)    [<EmbeddingDistance.COSINE: 'cosine'>,     <EmbeddingDistance.EUCLIDEAN: 'euclidean'>,     <EmbeddingDistance.MANHATTAN: 'manhattan'>,     <EmbeddingDistance.CHEBYSHEV: 'chebyshev'>,     <EmbeddingDistance.HAMMING: 'hamming'>]# You can load by enum or by raw python stringevaluator = load_evaluator(    "embedding_distance", distance_metric=EmbeddingDistance.EUCLIDEAN)Select Embeddings to Use​The constructor uses OpenAI embeddings by default, but you can configure this however you want. Below, use huggingface local embeddingsfrom langchain.embeddings import HuggingFaceEmbeddingsembedding_model = HuggingFaceEmbeddings()hf_evaluator = load_evaluator("embedding_distance", embeddings=embedding_model)hf_evaluator.evaluate_strings(prediction="I shall go", reference="I shan't go")    {'score': 0.5486443280477362}hf_evaluator.evaluate_strings(prediction="I shall go", reference="I will go")    {'score': 0.21018880025138598}1. Note: When it comes to semantic similarity, this often gives better results than older string distance metrics (such as those in the [StringDistanceEvalChain](https://api.python.langchain.com/en/latest/evaluation/langchain.evaluation.string_distance.base.StringDistanceEvalChain.html#langchain.evaluation.string_distance.base.StringDistanceEvalChain)), though it tends to be less reliable than evaluators that use the LLM directly (such as the [QAEvalChain](https://api.python.langchain.com/en/latest/evaluation/langchain.evaluation.qa.eval_chain.QAEvalChain.html#langchain.evaluation.qa.eval_chain.QAEvalChain) or [LabeledCriteriaEvalChain](https://api.python.langchain.com/en/latest/evaluation/langchain.evaluation.criteria.eval_chain.LabeledCriteriaEvalChain.html#langchain.evaluation.criteria.eval_chain.LabeledCriteriaEvalChain)) PreviousCustom String EvaluatorNextExact MatchSelect the Distance MetricSelect Embeddings to Use