Thanks for the feedback. After checking the loadVocabulary() method, the Dictionary(uniqueKeysWithValues: zip(words, values) is never initialized and the thread runs forever. The 2 arguments -> word: [String.Subsequence] and value: Range<Int> seems correct after printing them. Thus, the issue might come from the Dictionary(uniqueKeysWithValues: ) initialization. I'll give a try to see how long it takes to build the dictionary. Alexis