Memory-Efficient FastText: A Comprehensive Approach Using Double-Array Trie Structures and Mark-Compact Memory Management

Abstract: FastText has established itself as a fundamental algorithm for learning word representations, demonstrating exceptional capability in handling out-of-vocabulary words through character-level n-gram embeddings. However, its hash-based bucketing mechanism introduces critical limitations for large-scale industrial deployment: hash collisions cause semantic drift, and memory requirements become prohibitively expensive when dealing with real-world vocabularies containing millions of terms. This paper presents a comprehensive memory optimization framework that fundamentally reimagines FastText's memory management through the integration of double-array trie (DA-trie) structures and mark-compact garbage collection principles. Our approach leverages the linguistic insight that n-grams sharing common prefixes or suffixes exhibit highly correlated embeddings due to co-occurrence patterns in natural language. By systematically identifying and merging semantically similar embeddings based on structural relationships, we achieve compression ratios of 4:1 to 10:1 while maintaining near-perfect embedding quality. The algorithm consists of four sophisticated phases: prefix trie construction with embedding mapping, prefix-based similarity compression, suffix-based similarity compression, and mark-compact memory reorganization. Comprehensive experiments on a 30-million Chinese vocabulary dataset demonstrate memory reduction from over 100GB to approximately 30GB with negligible performance degradation. Our industrial deployment results show significant cost reduction, faster loading times, and improved model reliability through the elimination of hash collision artifacts. Code and experimental implementations are available at: https://github.com/initial-d/me_fasttext