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"""
This is a more complex example on performing clustering on large scale dataset.
This examples find in a large set of sentences local communities, i.e., groups of sentences that are highly
similar. You can freely configure the threshold what is considered as similar. A high threshold will
only find extremely similar sentences, a lower threshold will find more sentence that are less similar.
A second parameter is 'min_community_size': Only communities with at least a certain number of sentences will be returned.
The method for finding the communities is extremely fast, for clustering 50k sentences it requires only 5 seconds (plus embedding comuptation).
In this example, we download a large set of questions from Quora and then find similar questions in this set.
"""
from sentence_transformers import SentenceTransformer, util
import os
import csv
import time
# Model for computing sentence embeddings. We use one trained for similar questions detection
model = SentenceTransformer('all-MiniLM-L6-v2')
# We donwload the Quora Duplicate Questions Dataset (https://www.quora.com/q/quoradata/First-Quora-Dataset-Release-Question-Pairs)
# and find similar question in it
url = "http://qim.fs.quoracdn.net/quora_duplicate_questions.tsv"
dataset_path = "quora_duplicate_questions.tsv"
max_corpus_size = 50000 # We limit our corpus to only the first 50k questions
# Check if the dataset exists. If not, download and extract
# Download dataset if needed
if not os.path.exists(dataset_path):
print("Download dataset")
util.http_get(url, dataset_path)
# Get all unique sentences from the file
corpus_sentences = set()
with open(dataset_path, encoding='utf8') as fIn:
reader = csv.DictReader(fIn, delimiter='\t', quoting=csv.QUOTE_MINIMAL)
for row in reader:
corpus_sentences.add(row['question1'])
corpus_sentences.add(row['question2'])
if len(corpus_sentences) >= max_corpus_size:
break
corpus_sentences = list(corpus_sentences)
print("Encode the corpus. This might take a while")
corpus_embeddings = model.encode(corpus_sentences, batch_size=64, show_progress_bar=True, convert_to_tensor=True)
print("Start clustering")
start_time = time.time()
#Two parameters to tune:
#min_cluster_size: Only consider cluster that have at least 25 elements
#threshold: Consider sentence pairs with a cosine-similarity larger than threshold as similar
clusters = util.community_detection(corpus_embeddings, min_community_size=25, threshold=0.75)
print("Clustering done after {:.2f} sec".format(time.time() - start_time))
#Print for all clusters the top 3 and bottom 3 elements
for i, cluster in enumerate(clusters):
print("\nCluster {}, #{} Elements ".format(i+1, len(cluster)))
for sentence_id in cluster[0:3]:
print("\t", corpus_sentences[sentence_id])
print("\t", "...")
for sentence_id in cluster[-3:]:
print("\t", corpus_sentences[sentence_id])
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