26838 research outputs found
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Topic modeling for conversations for mental health helplines with utterance embedding
Get PDFConversations with topics that are locally contextual often produces incoherent topic modeling results using standard methods. Splitting a conversation into its individual utterances makes it possible to avoid this problem. However, with increased data sparsity, different methods need to be considered. Baseline bag-of-word topic modeling methods for regular and short-text, as well as topic modeling methods using transformer-based sentence embeddings were implemented. These models were evaluated on topic coherence and word embedding similarity. Each method was trained using single utterances, segments of the conversation, and on the full conversation. The results showed that utterance-level and segment-level data combined with sentence embedding methods performs better compared to other non-sentence embedding methods or conversation-level data. Among the sentence embedding methods, clustering using HDBScan showed the best performance. We suspect that ignoring noisy utterances is the reason for better topic coherence and a relatively large improvement in topic word similarity
Accelerating matroid optimization through fast imprecise oracles
Get PDFQuerying complex models for precise information (e.g. traffic models, database systems, large ML models) often entails intense computations and results in long response times. Thus, weaker models which give imprecise results quickly can be advantageous, provided inaccuracies can be resolved using few queries to a stronger model. In the fundamental problem of computing a maximum-weight basis of a matroid, a well-known generalization of many combinatorial optimization problems, algorithms have access to a clean oracle to query matroid information. We additionally equip algorithms with a fast but dirty oracle modelling an unknown, potentially different matroid. We design and analyze practical algorithms which only use few clean queries w.r.t. the quality of the dirty oracle, while maintaining robustness against arbitrarily poor dirty matroids, approaching the performance of classic algorithms for the given problem. Notably, we prove that our algorithms are, in many respects, best-possible. Further, we outline extensions to other matroid oracle types, non-free dirty oracles and other matroid problems
Competitive query minimization for stable matching with one-sided uncertainty
Get PDFWe study the two-sided stable matching problem with one-sided uncertainty for two sets of agents A and B, with equal cardinality. Initially, the preference lists of the agents in A are given but the preferences of the agents in B are unknown. An algorithm can make queries to reveal information about the preferences of the agents in B. We examine three query models: comparison queries, interviews, and set queries. Using competitive analysis, our aim is to design algorithms that minimize the number of queries required to solve the problem of finding a stable matching or verifying that a given matching is stable (or stable and optimal for the agents of one side). We present various upper and lower bounds on the best possible competitive ratio as well as results regarding the complexity of the offline problem of determining the optimal query set given full information
Exact synthesis of multiqutrit clifford-cyclotomic circuits
Get PDFIt is known that the matrices that can be exactly represented by a multiqubit circuit over the Toffoli+Hadamard, Clifford+T, or, more generally, Clifford-cyclotomic gate set are precisely the unitary matrices with entries in the ring Z[1/2,ζk], where k is a positive integer that depends on the gate set and ζk is a primitive 2k-th root of unity. In the present paper, we establish an analogous correspondence for qutrits. We define the multiqutrit Clifford-cyclotomic gate set of degree 3k by extending the classical qutrit gates X, CX, and CCX with the Hadamard gate H and the Tk gate Tk=diag(1,ωk,ω2k), where ωk is a primitive 3k-th root of unity. This gate set is equivalent to the qutrit Toffoli+Hadamard gate set when k=1, and to the qutrit Clifford+Tk gate set when k>1. We then prove that a 3n×3n unitary matrix U can be represented by an n-qutrit circuit over the Clifford-cyclotomic gate set of degree 3k if and only if the entries of U lie in the ring Z[1/3,ωk]
Quantum sieving for code-based cryptanalysis and Its limitations for ISD
Get PDFSieving using near-neighbor search techniques is a well-known method in lattice-based cryptanalysis, yielding the current best runtime for the shortest vector problem in both the classical [BDGL16] and quantum [BCSS23] setting. Recently, sieving has also become an important tool in code-based cryptanalysis. Specifically, using a sieving subroutine, [GJN23, DEEK24] presented a variant of the information-set decoding (ISD) framework, which is commonly used for attacking cryptographically relevant instances of the decoding problem. The resulting sieving-based ISD framework yields complexities close to the best-performing classical algorithms for the decoding problem such as [BJMM12, BM18]. It is therefore natural to ask how well quantum versions perform.
In this work, we introduce the first quantum algorithms for code sieving by designing quantum variants of the aforementioned sieving subroutine. In particular, using quantum-walk techniques, we provide a speed-up over the best known classical algorithm from [DEEK24] and over a variant using Grover's algorithm [Gro96]. Our quantum-walk algorithm exploits the structure of the underlying search problem by adding a layer of locality-sensitive filtering, inspired by the quantum-walk algorithm for lattice sieving from [CL21]. We complement our asymptotic analysis of the quantum algorithms with numerical results, and observe that our quantum speed-ups for code sieving behave similarly as those observed in lattice sieving.
In addition, we show that a natural quantum analog of the sieving-based ISD framework does not provide any speed-up over the first presented quantum ISD algorithm [Ber10]. Our analysis highlights that the framework should be adapted in order to outperform the state-of-the-art of quantum ISD algorithms [KT17, Kir18]
usethesource/vallang
No full textGeneric immutable recursive data representation API targeted at source code models and more
Live game design: You make the rules
Get PDFDesigning games is difficult and time-consuming. To speed up and
simplify the design process, we have developed the Vie app [4]. Vie
is a visual programming language for quickly creating 2D game
prototypes [2, 3]. After a brief introduction, you can create your
own game rules and instantly see your ideas come to life. To get
you started, you will receive assignments and a handy cheat sheet
Calculating radio emissions of positive streamer phenomena using 3D simulations
Get PDFWe study radio emissions from positive streamers in air using 3D simulations, from which the radiated electric field is computed by solving Jefimenko’s equations. The simulations are performed at (Formula presented.) using two photoionization methods: the Helmholtz approximation for a photon density and a Monte Carlo method using discrete photons, with the latter being the most realistic. We consider cases with single streamers, streamer branching, streamers interacting with preionization and streamer-streamer encounters. We do not observe a strong VHF radio signal during or after branching, which is confirmed by lab experiments. This indicates that the current inside a streamer discharge evolves approximately continuously during branching. On the other hand, stochastic fluctuations in streamer propagation due to Monte Carlo photoionization lead to more radio emission being emitted at frequencies of 100 MHz and above. Another process that leads to such high-frequency emission is the interaction of a streamer with a weakly preionized region, which can be present due to a previous discharge. In agreement with previous work, we observe the strongest and highest-frequency emission from streamer encounters. The amount of total energy that is radiated seems to depend primarily on the background electric field, and less on the particular streamer evolution. Finally, we present approximations for the maximal current along a streamer channel and a fit formula for a streamer's current moment