In the classical survivable network design problem (SNDP), we are given an undirected graph G=(V,E) with costs on edges and a connectivity requirement k(s,t) for each pair of vertices. The goal is to find a minimum-cost subgraph H⊆ G such that every pair (s,t) is connected by k(s,t) edge or (openly) vertex disjoint paths, abbreviated as EC-SNDP and VC-SNDP, respectively. The seminal result of Jain [FOCS’98, Combinatorica’01] gives a 2-approximation algorithm for EC-SNDP, and a decade later, an O(k 3 log n )-approximation algorithm for VC-SNDP, where k is the largest connectivity requirement, was discovered by Chuzhoy and Khanna [FOCS’09, Theory Comput.’12]. While there is a rich literature on point-to-point settings of SNDP, the viable case of connectivity between subsets is still relatively poorly understood. This article concerns the generalization of EC-SNDP into the subset-to-subset setting, namely Group EC-SNDP. We develop a framework, which yields the first non-trivial (true) approximation algorithm for Group EC-SNDP. Previously, only a bicriteria approximation algorithm is known for Group EC-SNDP [Chalermsook, Grandoni, and Laekhanukit, SODA’15], and a true approximation algorithm is known only for the single-source variant with connectivity requirement k(S,T) ∈ { 0,1,2} [Gupta, Krishnaswamy, and Ravi, SODA’10; Khandekar, Kortsarz, and Nutov, FSTTCS’09 and Theor. Comput. Sci.’12]. On the negative side, in terms of the number of connectivity demands q , we give an Ω (q /log q )-hardness result for large k , complementing the previous inapproximability results, e.g., hardness in terms of k : k 1/5-ɛ -hardness [Cheriyan et al., SODA’12; Laekhanukit, SODA’14; Chalermsook et al., SODA’15; Manurangsi, IPL’19]; hardness in terms of n : 2 log 1-ɛ n -hardness [Chalermsook et al., SODA’15].

Recently, the remarkable advance of the Large Language Model (LLM) has inspired researchers to transfer its extraordinary reasoning capability to both vision and language data. However, the prevailing approaches primarily regard the visual input as a prompt and focus exclusively on optimizing the text generation process conditioned upon vision content by a frozen LLM. Such an inequitable treatment of vision and language heavily constrains the model's potential. In this paper, we break through this limitation by representing both vision and language in a unified form. Specifically, we introduce a well-designed visual tokenizer to translate the non-linguistic image into a sequence of discrete tokens like a foreign language that LLM can read. The resulting visual tokens encompass high-level semantics worthy of a word and also support dynamic sequence length varying from the image. Coped with this tokenizer, the presented foundation model called LaVIT can handle both image and text indiscriminately under the same generative learning paradigm. This unification empowers LaVIT to serve as an impressive generalist interface to understand and generate multi-modal content simultaneously. Extensive experiments further showcase that it outperforms the existing models by a large margin on massive vision-language tasks. Our code and models are available at https://github.com/jy0205/LaVIT.

Dialect recognition aims to recognize dialect categories in utterances, which has been applied in many audio applications. Recently, various Time Delayed Neural Network (TDNN) based AI models are proposed to solve dialect recognition problems, such as D-TDNN, DMC-TDNN, and ECAPA-TDNN, however, most of them only perform temporal attention in the last statistical pooling layer of the TDNN network, which ignores the importance of simultaneously capturing both frequency and temporal key information in utterances under different receptive fields. In contrast, we introduce a hybrid attention mechanism in both the temporal and frequency domain, called the TF-attention module, which adaptively pays more attention to the indeed important frames and the frame-level important information under different receptive fields for dialect recognition. Moreover, we are the first to introduce a dynamic architecture mechanism in the field of dialect recognition to dynamically reduce the computational cost and the number of parameters of models. We evaluate the proposed dynamic TF-TDNN on the OLR challenge AP20-OLR-dialect task and achieve State-Of-The-Art (SOTA) performance with fewer model parameters.

In the classical survivable network design problem (SNDP), we are given an undirected graph $G-(V,E)$ with costs on edges and a connectivity requirement $k(5,t)$ for each pair of vertices. The goal is to find a minimum-cost subgraph $H\sqsubseteq G$ such that every pair $(s,t)$ are connected by $k(s,t)$ edge or (openly) vertex disjoint paths, abbreviated as EC-SNDP and VC-SNDP, respectively. The seminal result of Jain [FOCS’98, Combinatorica’01] gives a 2-approximation algorithm for EC-SNDP, and a decade later, an $O(k^{3}\log n)-$ approximation algorithm for VC-SNDP, where k is the largest connectivity requirement, was discovered by Chuzhoy and Khanna [FOCS’09, Theory Comput’12]. While there is a rich literature on point-to-point settings of SNDP, the viable case of connectivity between subsets is still relatively poorly understood. This paper concerns the generalization of SNDP into the subset-to-subset setting, namely Group EC-SNDR We develop the framework, which yields the first non-trivial (true) approximation algorithm for Group. EC-SNDE Previously only a bicriteria approximation algorithm is known for Group EC-SNDP [Chalermsook, Grandoni, and Laekhanukit, SODA’15l, and a true approximation algorithm is known only for the single-source variant with connectivity requirement $k(S,T)\in\{0,1,2\}$ [Gupta, Krishnaswamy, and Ravi, SODA’10; Khandekar, Kortsarz, and Nutov, FSTTCS’09 and Theor Comput. Sci’12].

In the k-outconnected directed Steiner tree problem (k-DST), we are given an n-vertex directed graph G = (V,E) with edge costs, a connectivity requirement k, a root r ∈ V and a set of terminals T ⊆ V. The goal is to find a minimum-cost subgraph H ⊆ G that has k edge-disjoint paths from the root vertex r to every terminal t ∈ T. The problem is NP-hard, and inapproximability results are known in several parameters, e.g., hardness in terms of n: log^{2-ε}n-hardness for k = 1 [Halperin and Krauthgamer, STOC'03], 2^{log^{1-ε}n}-hardness for general case [Cheriyan, Laekhanukit, Naves and Vetta, SODA'12], hardness in terms of k [Cheriyan et al., SODA'12; Laekhanukit, SODA'14; Manurangsi, IPL'19] and hardness in terms of |T| [Laekhanukit, SODA'14]. In this paper, we show the approximation hardness of k-DST for various parameters. - Ω(|T|/log |T|)-approximation hardness, which holds under the standard complexity assumption NP≠ ZPP. The inapproximability ratio is tightened to Ω(|T|) under the Strongish Planted Clique Hypothesis [Manurangsi, Rubinstein and Schramm, ITCS 2021]. The latter hardness result matches the approximation ratio of |T| obtained by a trivial approximation algorithm, thus closing the long-standing open problem. - Ω(2^{k/2} / k)-approximation hardness for the general case of k-DST under the assumption NP≠ZPP. This is the first hardness result known for survivable network design problems with an inapproximability ratio exponential in k. - Ω((k/L)^{L/4})-approximation hardness for k-DST on L-layered graphs for L ≤ O(log n). This almost matches the approximation ratio of O(k^{L-1}⋅ L ⋅ log |T|) achieved in O(n^L)-time due to Laekhanukit [ICALP'16]. We further extend our hardness results in terms of |T| to the undirected cases of k-DST, namely the single-source k-vertex-connected Steiner tree and the k-edge-connected group Steiner tree problems. Thus, we obtain Ω(|T|/log |T|) and Ω(|T|) approximation hardness for both problems under the assumption NP≠ ZPP and the Strongish Planted Clique Hypothesis, respectively. This again matches the upper bound obtained by trivial algorithms.

Keyword Spotting (KWS) is a task that detects predefined keywords in a stream of audio. Although state-of-the-art deep neural networks perform well on KWS, they are not robust against out-of-vocabulary (OOV) samples because of their over-reliance on labeled data and the great imbalance between in-vocabulary (IV) and OOV data resulting from the infinity of OOV data. Besides, some end-to-end(E2E) KWS try to treat it as a multi-classification task, rejecting most OOV samples through posterior processing, but they cannot ensure the classifier can always be sure that its judgment is correct and keywords are usually too short to extract many representative features. To address these issues, we introduce a KWS model that can keep robustness on OOV samples by learning confidence estimates of the model. Confidence estimation is output by the self-attentional confidence branch, which can focus on single keyword in context. And we propose a loss function, named Triplet Correction Loss, which learning confidence estimation to improve the reliability of the model without relying on labeled data. Compared with the state-of-the-art methods, our proposed network increases 1.80%(V2-25) and 7.63%(Librispeech) accuracy on OOV samples, while keeping the high accuracy on IV dataset. We also provide ablation study to prove that our method is effective.

We present fully polynomial-time (deterministic or randomised) approximation schemes for Holant problems, defined by a non-negative constraint function satisfying a generalised second-order recurrence modulo in a couple of exceptional cases. As a consequence, any non-negative Holant problem on cubic graphs has an efficient approximation algorithm unless the problem is equivalent to approximately counting perfect matchings, a central open problem in the area. This is in sharp contrast to the computational phase transition shown by two-state spin systems on cubic graphs. Our main technique is the recently established connection between zeros of graph polynomials and approximate counting.

The detection and tracking of road signs plays a critical role in various autopilot application. Utilizing convolutional neural networks(CNN) mostly incurs a big run-time overhead in feature extraction and object localization. Although Klaman filter(KF) is a commonly-used tracker, it is likely to be impacted by omitted objects in the detection step. In this paper, we designed a high-efficient detector that combines ThunderNet and Region Growing Detector(RGD) to detect road signs, and built a fusion model of long short term memory network (LSTM) and KF in the state estimation and the color histogram. The experimental results demonstrate that the proposed method improved the state estimation accuracy by 6.4% and enhanced the Frames Per Second(FPS) to 41.

We propose an EM-based framework for learning Plackett-Luce model and its mixtures from partial orders. The core of our framework is the efficient sampling of linear extensions of partial orders under Plackett-Luce model. We propose two Markov Chain Monte Carlo (MCMC) samplers: Gibbs sampler and the generalized repeated insertion method tuned by MCMC (GRIM-MCMC), and prove the efficiency of GRIM-MCMC for a large class of preferences.Experiments on synthetic data show that the algorithm with Gibbs sampler outperforms that with GRIM-MCMC. Experiments on real-world data show that the likelihood of test dataset increases when (i) partial orders provide more information; or (ii) the number of components in mixtures of PlackettLuce model increases.

We give a fully polynomial-time approximation scheme (FPTAS) to count the number of independent sets on almost every $Δ$-regular bipartite graph if $Δ\ge 53$. In the weighted case, for all sufficiently large integers $Δ$ and weight parameters $λ=\tildeΩ\left(\frac{1}Δ\right)$, we also obtain an FPTAS on almost every $Δ$-regular bipartite graph. Our technique is based on the recent work of Jenssen, Keevash and Perkins (SODA, 2019) and we also apply it to confirm an open question raised there: For all $q\ge 3$ and sufficiently large integers $Δ=Δ(q)$, there is an FPTAS to count the number of $q$-colorings on almost every $Δ$-regular bipartite graph.

We present fully polynomial-time (deterministic or randomised) approximation schemes for Holant problems, defined by a non-negative constraint function satisfying a generalised second order recurrence modulo a couple of exceptional cases. As a consequence, any non-negative Holant problem on cubic graphs has an efficient approximation algorithm unless the problem is equivalent to approximately counting perfect matchings, a central open problem in the area. This is in sharp contrast to the computational phase transition shown by 2-state spin systems on cubic graphs. Our main technique is the recently established connection between zeros of graph polynomials and approximate counting. We also use the “winding” technique to deduce the second result on cubic graphs.

We give a fully polynomial-time approximation scheme (FPTAS) to count the number of $q$-colorings for $k$-uniform hypergraphs with maximum degree $\Delta$ if $k\ge 28$ and $q > 357 \Delta^{\frac{14}{k-14}}$. We also obtain a polynomial-time almost uniform sampler if $q>931 \Delta^{\frac{16}{k-16/3}}$. These are the first approximate counting and sampling algorithms in the regime $q\ll\Delta$ (for large $\Delta$ and $k$) without any additional assumptions. Our method is based on the recent work of Moitra (STOC, 2017). One important contribution of ours is to remove the dependency of $k$ and $\Delta$ in Moitra's approach.

We give a fully polynomial-time approximation scheme (FPTAS) to count the number of q-colorings for k-uniform hypergraphs with maximum degree Δ if k≥ 28 and q > 315Δ14/k−14. We also obtain a polynomial-time almost uniform sampler if q>798Δ16/k−16/3. These are the first approximate counting and sampling algorithms in the regime q≪Δ (for large Δ and k) without any additional assumptions. Our method is based on the recent work of Moitra (STOC, 2017). One important contribution of ours is to remove the dependency of k and Δ in Moitra’s approach.

Both capacity and energy efficiency are crucial for next-generation wireless networks. This paper investigates energy efficiency in cooperative cellular networks. Based on the double auction theory, we model the optimal relay assignment problem, which aims at improving the performance of cell-edge users (CEUs) with energy efficiency optimization. In the proposed auction-based model, the selfish nature of users is taken into consideration, which means users in the idle state are unwilling to relay the information for active CEUs unless they are paid enough. Therefore, we use mark-up to determine the bid and ask. Furthermore, the energy efficiency (EE) is defined and the model for optimizing the EE is built. An energy-efficient maximum weighted matching algorithm (EE-MWM) is proposed to solve the EE optimization problem. Finally, the performance of EE-MWM is evaluated in terms of EE, capacity and social welfare, which shows that EE-MWM can greatly improve the performance of cooperative cellular networks.

In this paper, we propose a relay selection method, Maximum Throughput Relay Selection Algorithm (MTRSA) for wireless networks. Based on the derivation of direct and cooperative communications, MTRSA takes both MAC overhead and collision into consideration for maximizing the system throughput. In addition, the analytical derivation and proposed relay selection algorithm support both amplify-and-forward (AF) and decode-and-forward (DF). Numerical results and simulations are provided to validate the efficiency of our algorithm.

Recently, as it can increase the capacity of wireless networks greatly through spatial diversity by taking advantage of antennas on other nodes, cooperative communication (CC) has been obtaining more and more attention. However, as the selfish nature, the wireless node may be unwilling to serve as relay node if they can't get the corresponding reward. In this paper, we constructs a real double-auction scenario between source nodes and relay nodes instead of idealized truthful market which may obtain relatively lower system performance. We consider the system performance involving (1) successful source-relay pairs, (2) system capacity and (3) social welfare (SW). We transform the double auction-based optimal relay assignment problem into Maximum Matching (MM) and Maximum Weighted Matching (MWM) problem respectively and solve them using corresponding algorithms. Extensive experiments show that this mechanism can achieve higher system efficiency than truthful auction.

Object tracking is a major technique in image processing and computer vision. In this paper, we propose a new robust feature-based tracking scheme by employing adaptive classifiers to match the detected keypoints in consecutive frames. The novelty of this paper is that the design of online boosting is combined with the invariance of local features so that the classifier-based descriptions are formed in association with the scale and rotation information. Furthermore, we introduce a sample weighting mechanism in the on-line classifier updating, for the subsequent tracking. Experimental results demonstrate the robustness and accuracy of our proposed technique.

This paper introduces a topology based affine invariant descriptor for maximally stable extremal regions (MSERs). The popular SIFT descriptor computes the texture information on a grey-scale patch. Instead our descriptor use only the topology and geometric information among MSERs so that features can be rapidly matched regardless of the texture in the image patch. Based on the ellipses fitting for the detected MSERs, geometric affine invariants between ellipses pair are extracted as the descriptors. Finally topology based voting selector is designed to achieve the best correspondences. Experiment shows that our descriptor is not only computational faster than SIFT descriptor, but also has better performance on wide angle of view and nonlinear illumination change. In addition, our descriptor shows a good result on multi sensor images registration.