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Evolutionary algorithms are popular algorithms for multiobjective optimisation (also called Pareto optimisation) as they use a population to store trade-offs between different objectives. Despite their popularity, the theoretical foundation of multiobjective evolutionary optimisation (EMO) is still in its early development. Fundamental questions such as the benefits of the crossover operator are still not fully understood.

We provide a theoretical analysis of well-known EMO algorithms GSEMO and NSGA-II to showcase the possible advantages of crossover. We propose a class of problems on which these EMO algorithms using crossover find the Pareto set in expected polynomial time. In sharp contrast, they and many other EMO algorithms without crossover require exponential time to even find a single Pareto-optimal point. This is the first example of an exponential performance gap through the use of crossover for the widely used NSGA-II algorithm.

AAAI 2023

A Proof that Using Crossover Can Guarantee Exponential Speed-Ups in Evolutionary Multi-Objective Optimisation

recombination

multi-objective optimisation

evolutionary computation

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ECAI 2020

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The purpose of the AAAI conference series is to promote research in Artificial Intelligence (AI) and foster scientific exchange between researchers, practitioners, scientists, students, and engineers across the entirety of AI and its affiliated disciplines. AAAI-23 is the Thirty-Seventh AAAI Conference on Artificial Intelligence. The theme of this conference is to create collaborative bridges within and beyond AI. Like previous AAAI conferences, AAAI-23 will feature technical paper presentations, special tracks, invited speakers, workshops, tutorials, poster sessions, senior member presentations, competitions, and exhibit programs, and two new activities: a Bridge Program and a Lab Program. Many of these activities are tailored to the theme of bridges and all are selected according to the highest standards, with additional programs for students and young researchers. 
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The purpose of the AAAI conference series is to promote research in Artificial Intelligence (AI) and foster scientific exchange between researchers, practitioners, scientists, students, and engineers across the entirety of AI and its affiliated disciplines.

Deep generative models are effective in style transfer. 
Previous methods learn one or several specific artist-style from a collection of artworks.
These methods not only homogenize the artist-style of different artworks of the same artist but also lack generalization for the unseen artists.
To solve these challenges, we propose a double-style transferring module (DSTM).
It extracts different artist-style and artwork-style from different artworks (even untrained) and preserves the intrinsic diversity between different artworks of the same artist.
DSTM swaps the two styles in the adversarial training and encourages realistic image generation given arbitrary style combinations.
However, learning style from single artwork can often cause over-adaption to it, resulting in the introduction of structural features of style image.
We further propose an edge enhancing module (EEM) which derives edge information from multi-scale and multi-level features to enhance structural consistency.
We broadly evaluate our method across six large-scale benchmark datasets.
Empirical results show that our method achieves arbitrary artist-style and artwork-style extraction from a single artwork, and effectively avoids introducing the style image’s structural features.
Our method improves the state-of-the-art deception rate from 58.9% to 67.2% and the average FID from 48.74 to 42.83.

Preserving Structural Consistency in Arbitrary Artist and Artwork Style Transfer

The decomposition-based multi-objective evolutionary algorithm (MOEA/D) transforms a multi-objective optimization problem (MOP) into a set of single-objective subproblems for collaborative optimization. Mismatches between subproblems and solutions can lead to severe performance degradation of MOEA/D. Most existing mismatch coping strategies only work when the L∞ scalarization is used. A mismatch coping strategy that can use any Lp scalarization, even when facing MOPs with non-convex Pareto fronts, is of great significance for MOEA/D. This paper uses the global replacement (GR) as the backbone. We analyze how GR can no longer avoid mismatches when L∞ is replaced by another Lp with p ∈ [1, ∞), and find that the Lp-based (1 ≤ p < ∞) subproblems having inconsistently large preference regions. When p is set to a small value, some middle subproblems have very small preference regions so that their direction vectors cannot pass through their corresponding preference regions. Therefore, we propose a generalized Lp (GLp) scalarization to ensure that the subproblem’s direction vector passes through its preference region. Our theoretical analysis shows that GR can always avoid mismatches when using the GLp scalarization for any p ≥ 1. The experimental studies on various MOPs conform to the theoretical analysis.

A Generalized Scalarization Method for Evolutionary Multi-objective Optimization

It is possible for agents operating in a shared environment to interfere with one another. One mechanism of coordination is called Social Law. Enacting such a law in a multi-agent setting restricts agents' behaviors. Robustness, in this case, ensures that the agents do not harmfully interfere with each other and that each agent achieves its goals regardless of what other agents do. Previous work on social law verification examined only the case of boolean state variables. However, many real-world problems require reasoning with numeric variables. Moreover, numeric fluents allow a more compact representation of multiple planning problems.

In this paper, we develop a method to verify whether a given social law is robust via compilation to numeric planning. A solution to this compilation constitutes a counterexample to the robustness of the problem, i.e., evidence of cross-agent conflict. Thus, the social law is robust if and only if the proposed compilation is unsolvable. We empirically verify robustness in multiple domains using state-of-the-art numeric planners. Additionally, this compilation raises a challenge by generating a set of non-trivial numeric domains where unsolvability should be either proved or disproved.

Automated Verification of Social Laws in Numeric Settings

Semi-supervised learning (SSL) has been actively studied due to its ability to alleviate the reliance of deep learning models on labeled data. Although existing SSL methods based on pseudo-labeling strategies have made great progress, they rarely consider time-series data's intrinsic properties (e.g., temporal dependence). Learning representations by mining the inherent properties of time series has recently gained much attention. Nonetheless, how to utilize feature representations to design SSL paradigms for time series has not been explored. To this end, we propose a Time Series SSL framework via Temporal-Frequency Co-training (TS-TFC), leveraging the complementary information from two distinct views for unlabeled data learning. In particular, TS-TFC employs time-domain and frequency-domain views to train two deep neural networks simultaneously, and each view's pseudo-labels generated by label propagation in the representation space are adopted to guide the training of the other view's classifier. To enhance the discriminative of representations between categories, we propose a temporal-frequency supervised contrastive learning module, which integrates the learning difficulty of categories to improve the quality of pseudo-labels. Through co-training the pseudo-labels obtained from temporal-frequency representations, the complementary information in the two distinct views is exploited to enable the model to better learn the distribution of categories. Extensive experiments on 106 UCR datasets show that TS-TFC outperforms state-of-the-art methods, demonstrating the effectiveness and robustness of our proposed model.

Temporal-Frequency Co-Training for Time Series Semi-Supervised Learning

Existing natural language understanding (NLU) models often rely on dataset biases rather than intended task-relevant features to achieve high performance on specific datasets. As a result, these models perform poorly on datasets outside the training distribution. Some recent studies address the above issue by reducing the weights of biased samples during the training process. However, these methods still encode biased latent features in representations and neglect the dynamic nature of bias, which hinders model prediction. We propose an NLU debiasing method, named debiasing contrastive learning (DCT), to simultaneously alleviate the above problems based on contrastive learning. We devise a debiasing positive sampling strategy to mitigate biased latent features by selecting the least similar biased positive samples. We also propose a dynamic negative sampling strategy to capture the dynamic influence of biases by employing a bias-only model to dynamically select the most similar biased negative samples. We conduct experiments on three NLU benchmark datasets. Experimental results show that DCT outperforms state-of-the-art baselines on out-of-distribution datasets while maintaining in-distribution performance. We also verify that DCT can reduce biased latent features from the model’s representations.

Feature-Level Debiased Natural Language Understanding

We consider a seller faced with buyers which have the ability to delay their decision, which we call patience.
Each buyer's type is composed of value and patience, and it is sampled i.i.d. from a distribution.
The seller, using posted prices, would like to maximize her revenue from selling to the buyer. 
In this paper, we formalize this setting and characterize the resulting Stackelberg equilibrium, where the seller first commits to her strategy, and then the buyers best respond. Following this, we show how to compute both the optimal pure and mixed strategies. 
We then consider a learning setting, where the seller does not have access to the distribution over buyer's types. Our main results are the following. We derive a sample complexity bound for the learning of an approximate optimal pure strategy, by computing the fat-shattering dimension of this setting. Moreover, we provide a general sample complexity bound for the approximate optimal mixed strategy. 
We also consider an online setting and derive a vanishing regret bound with respect to both the optimal pure strategy and the optimal mixed strategy. 

Learning Revenue Maximization using Posted Prices for Stochastic Strategic Patient Buyers

This paper introduces SigMaNet, a generalized Graph Convolutional Network (GCN) capable of handling both undirected and directed graphs with weights not restricted in sign nor magnitude. The cornerstone of SigMaNet is the Sign-Magnetic Laplacian ($L^{\sigma}$), a new Laplacian matrix that we introduce ex novo in this work.
$L^{\sigma}$ allows us to bridge a gap in the current literature by extending the theory of spectral GCNs to (directed) graphs with both positive and negative weights. $L^{\sigma}$ exhibits several desirable properties not enjoyed by other Laplacian matrices on which several state-of-the-art architectures are based, among which encoding the edge direction and weight in a clear and natural way that is not negatively affected by the weight magnitude.
$L^{\sigma}$ is also completely parameter-free, which is not the case of other Laplacian operators such as, e.g., the Magnetic Laplacian.
The versatility and the performance of our proposed approach is amply demonstrated via computational experiments. Indeed, our results show that, for at least a metric, SigMaNet achieves the best performance in 15 out of 21 cases and either the first- or second-best performance in 21 cases out of 21, even when compared to architectures that are either more complex or that, due to being designed for a narrower class of graphs, should---but do not---achieve a better performance.

SigMaNet: One Laplacian to Rule Them All

Quantitive structure activity relationship modeling is an important and challenging task in drug discovery. Despite recent advancements in leveraging graph neural network in this task, many of those work are unable to capture important information for molecules. Hence a novel graph neural network framework is proposed for the prediction of pharmacological activity in this paper. Features of the new method include SE(3)-/conformation invariance, chirality-awareness, and interpretability. The new framework replaces the classical message passing of attributes with the propagation of similarity scores between atom neighborhoods and a set of kernels. A comprehensive experiment that include well-curated datasets and evaluation metrics aligned with the real-world applications is conducted. This demonstrates the practical value of this new method. 


Interpretable Chirality-Aware Graph Neural Network for Quantitative Structure Activity Relationship Modeling in Drug Discovery

High-Throughput, High-Performance Deep Learning-driven Light Guide Plate Surface Visual Quality Inspection Tailored for Real-world Manufacturing Environments

A Proof that Using Crossover Can Guarantee Exponential Speed-Ups in Evolutionary Multi-Objective Optimisation

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Preserving Structural Consistency in Arbitrary Artist and Artwork Style Transfer

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