Collaborating Authors

On Uncensored Mean First-Passage-Time Performance Experiments with Multiwalk in $\mathbb{R}^p$: a New Stochastic Optimization Algorithm Artificial Intelligence

A rigorous empirical comparison of two stochastic solvers is important when one of the solvers is a prototype of a new algorithm such as multiwalk (MWA). When searching for global minima in $\mathbb{R}^p$, the key data structures of MWA include: $p$ rulers with each ruler assigned $m$ marks and a set of $p$ neighborhood matrices of size up to $m(m-2)$, where each entry represents absolute values of pairwise differences between $m$ marks. Before taking the next step, a controller links the tableau of neighborhood matrices and computes new and improved positions for each of the $m$ marks. The number of columns in each neighborhood matrix is denoted as the neighborhood radius $r_n \le m-2$. Any variant of the DEA (differential evolution algorithm) has an effective population neighborhood of radius not larger than 1. Uncensored first-passage-time performance experiments that vary the neighborhood radius of a MW-solver can thus be readily compared to existing variants of DE-solvers. The paper considers seven test cases of increasing complexity and demonstrates, under uncensored first-passage-time performance experiments: (1) significant variability in convergence rate for seven DE-based solver configurations, and (2) consistent, monotonic, and significantly faster rate of convergence for the MW-solver prototype as we increase the neighborhood radius from 4 to its maximum value.

POTs: The revolution will not be optimized? Artificial Intelligence

Optimization systems infer, induce, and shape events in the real world to fulfill objective functions. Protective optimization technologies (POTs) reconfigure these events as a response to the effects of optimization on a group of users or local environment. POTs analyze how events (or lack thereof) affect users and environments, then manipulate these events to influence system outcomes, e.g., by altering the optimization constraints and poisoning system inputs.

Optimistic Distributionally Robust Optimization for Nonparametric Likelihood Approximation

Neural Information Processing Systems

The likelihood function is a fundamental component in Bayesian statistics. However, evaluating the likelihood of an observation is computationally intractable in many applications. In this paper, we propose a non-parametric approximation of the likelihood that identifies a probability measure which lies in the neighborhood of the nominal measure and that maximizes the probability of observing the given sample point. We show that when the neighborhood is constructed by the Kullback-Leibler divergence, by moment conditions or by the Wasserstein distance, then our optimistic likelihood can be determined through the solution of a convex optimization problem, and it admits an analytical expression in particular cases. We also show that the posterior inference problem with our optimistic likelihood approximation enjoys strong theoretical performance guarantees, and it performs competitively in a probabilistic classification task.

Interactive urban design generation and optimization


The first video shows the set-up and process of optimizing a simple parametric design for an neighborhood. The algorithm takes five fitness objectives into account: Solar comfort on the streets (weighted by pedestrian frequency); wind comfort; footfall through the neighborhood; access to the neighborhood, overall access to local transit stations; The latter two indicators are computed for the whole area, thus enabling to include a positive impact of the new quarter's spatial arrangement on the whole neighborhood as a goal dimension. By using our deep learning based predictions for solar and wind related measures, one iteration takes just about three seconds to be computed.

Sparse Manifold Clustering and Embedding

Neural Information Processing Systems

We propose an algorithm called Sparse Manifold Clustering and Embedding (SMCE) for simultaneous clustering and dimensionality reduction of data lying in multiple nonlinear manifolds. Similar to most dimensionality reduction methods, SMCE finds a small neighborhood around each data point and connects each point to its neighbors with appropriate weights. The key difference is that SMCE finds both the neighbors and the weights automatically. This is done by solving a sparse optimization problem, which encourages selecting nearby points that lie in the same manifold and approximately span a low-dimensional affine subspace. The optimal solution encodes information that can be used for clustering and dimensionality reduction using spectral clustering and embedding.