We revisit the problem of $n$-gram extraction in the differential privacy setting. In this problem, given a corpus of private text data, the goal is to release as many $n$-grams as possible while preserving user level privacy. Extracting $n$-grams is a fundamental subroutine in many NLP applications such as sentence completion, auto response generation for emails, etc. The problem also arises in other applications such as sequence mining, trajectory analysis, etc., and is a generalization of recently studied differentially private set union (DPSU) by Gopi et al. (2020). In this paper, we develop a new differentially private algorithm for this problem which, in our experiments, significantly outperforms the state-of-the-art. Our improvements stem from combining recent advances in DPSU, privacy accounting, and new heuristics for pruning in the tree-based approach initiated by Chen et al. (2012).

We revisit the problem of n -gram extraction in the differential privacy setting. In this problem, given a corpus of private text data, the goal is to release as many n -grams as possible while preserving user level privacy. Extracting n -grams is a fundamental subroutine in many NLP applications such as sentence completion, auto response generation for emails, etc. The problem also arises in other applications such as sequence mining, trajectory analysis, etc., and is a generalization of recently studied differentially private set union (DPSU) by Gopi et al. (2020). In this paper, we develop a new differentially private algorithm for this problem which, in our experiments, significantly outperforms the state-of-the-art.

Dynamic Potential Search (DPS) is a recently introduced search algorithm that returns a bounded-suboptimal cost solution. DPS orders nodes in the open-list based on their potential which is a combination of both the g - and h -values of a node. In this paper we study the behavior of DPS on weighted graphs. In particular, we develop a new variant of DPS, called DPSU which calculates the potential by counting one for each edge regardless of its costs. We develop an eager version and a restrained version of DPSU. We then compare all these algorithms on a number of weighted graphs and study the pros and cons of each of them.