Science & Mathematics

Analytical global placement requires a differentiable wirelength objective that accurately reflects routed interconnect cost. The widely used half-perimeter wirelength (HPWL) is efficient but overlooks the internal topology of multi-pin nets. The rectilinear Steiner minimum tree (RSMT) provides higher fidelity, but its underlying decision problem is NP-complete, and its discrete construction precludes direct use in gradient-based optimization. The rectilinear minimum spanning tree (RMST) offers a polynomial-time alternative, but remains nondifferentiable because of minimization over discrete spanning trees. To address these limitations, we present DiffRMST, a fully differentiable RMST wirelength model for analytical global placement. DiffRMST combines spatial smoothing with a log-sum-exp relaxation to define a continuous distribution over spanning trees. Based on the Kirchhoff matrix-tree theorem, the partition function and edge marginals can be computed without explicit tree enumeration, enabling a closed-form topology-aware gradient for placement optimization. For efficient integration into analytical placement, we further develop a fused forward-backward operator with parallel CPU and GPU implementations. On the ISPD2019 benchmark suite, our method reduces RMST, RSMT, and routed wirelength by an average of 5.0%, 3.2%, and 3.5%, respectively, compared with the weighted-average baseline, while maintaining acceptable runtime. Furthermore, the GPU implementation achieves an average $14.7\times$ speedup in global placement over its eight-thread CPU counterpart.

Beam hopping technology enables LEO satellites to dynamically switch beam coverage positions, providing flexible resource allocation for non-uniformly distributed traffic demands. However, the severe spatial interference coupling among beams makes coordinated scheduling challenging. To address this problem, in this letter, we propose an interference-graph-aided multi-agent reinforcement learning approach that constructs an interference graph to capture beam coupling relationships and injects this structural prior into agent-side representation learning. Each beam agent aggregates information from interference neighbors via graph convolution before estimating local Q-values, which are then decomposed by the standard mixing network. Simulation results demonstrate that the proposed method achieves 34.4\% higher throughput than QMIX with more stable interference management, under non-uniform traffic and co-channel interference settings.

Robot swarms coordinate through directed, time-varying local communication links, some of which may be compromised to allow the transmission of arbitrary malicious data. We provide an algorithm that acts as a wrapper around robot communication---when a robot seeks to update its state using data from some incoming links, our wrapper provides a subset of trusted links whose data can be safely incorporated. It selects these links by testing a stream of trust values---data collected from an anomaly detector on each robot---using Safe Anytime-Valid Inference. We require only that the detector be better than chance. This wrapper ensures safe and performant autonomy by providing two powerful statistical guarantees: it uniformly excludes all compromised links for all time with high user-chosen probability, but nevertheless quickly learns to trust legitimate links. Both guarantees are vital to secure generic tasks, but no previous work provides them simultaneously without restrictive assumptions on connectivity structure or the number of compromised links that are not guaranteed in practice. We study our Safe Wrapper's performance in hardware for two contrasting tasks---neural implicit mapping and heading consensus---deploying on 3 LoCoBots and 8 GoPiGos, respectively. We provide simulations using trust values sampled from hardware to validate that our approach scales well to swarms of hundreds of robots.

Sparse variational Gaussian processes (SVGPs) are a widely used, principled approach to scalable Gaussian process modelling. Their success stems from their theoretically interpretable structure: they provide a lower bound on the marginal likelihood of the full GP while allowing scal- able stochastic optimization. Recent work has explored modifications of the posterior conditional distribution and has shown that such extensions can improve upon this well-established framework. In particular, introducing a block-diagonal structured scal- ing matrix leads to a tighter lower bound on the GP marginal likelihood. We investigate whether selecting blocks that tighten the variational objective improves test RMSE and NLL at a fixed inducing-point budget. Since the scaling matrix contributes to the variational lower bound through an upper bound on the log-determinant of the full residual covariance matrix, our work makes the following contributions. First, we introduce a simple, scalable, geometry-aware algorithm, with explicit computational complexity and low computational overhead, that recovers a large fraction of this log- determinant contribution by selecting an appropriate partition of the data. Second, we show how to train these models using a doubly stochastic optimization framework. Finally, we investigate how sparse GP methods based on alternative conditional posterior structures can be used to learn better hyperparameters and inducing points for SVGP.

This work presents SplatFlux, a feed-forward latent-to-4DGS framework for both video-based 4D reconstruction and conditional 4D generation. Our key observation is that observed videos and conditionally generated content can be represented in the same pretrained video latent space, allowing both tasks to be formulated as latent-to-4DGS decoding. To construct compact and temporally coherent 4D scenes, SplatFlux introduces a static-dynamic decoupled 4D Gaussian representation that explicitly predicts dynamic probabilities for Gaussian primitives. This representation separates static scene structures from moving regions, enabling complete 4D scene construction in a feed-forward manner through static aggregation and dynamic motion interpolation. To learn static-dynamic decomposition and dynamic Gaussian motion without costly annotations, we further develop an auxiliary distillation strategy that provides pseudo dynamic masks and optical-flow cues. Extensive experiments across 3D and 4D reconstruction and generation demonstrate that SplatFlux achieves state-of-the-art performance.

Low-cost multi-zone single-photon avalanche diode (SPAD) sensors provide compact time-of-flight measurements but are limited by sparse sampling and unreliable depth estimates near geometric discontinuities. This letter presents a reliability-aware reconstruction framework for V-shaped surfaces using two complementary TMF8821 acquisition configurations. Point-wise reliability is learned from sensor confidence, transient peak amplitude, and peak sharpness, and is incorporated into a graph-based depth optimization. The reconstructed geometry is evaluated by robust two-plane fitting and a perpendicular cross-section. Experiments on 60-degree, 90-degree, and 120-degree targets reduce the mean V-angle error from 11.21 degrees to 9.66 degrees (13.8%). For the representative 90-degree target, the combined point-to-plane RMSE decreases from 14.56 mm to 13.65 mm.

Recent advances in visuospatial understanding and agentic reasoning enable direct robotic manipulation with general-purpose multimodal models, but their embodied capabilities remain poorly understood. This paper systematically evaluate GPT-6 Astra for closed-loop robotic manipulation using a lightweight agent execution framework. We first probe three fundamental embodied capabilities-depth perception, embodied in-context learning, and tactile understanding-and demonstrate that the model can exploit depth information, acquire simple manipulation strategies from contextual demonstrations, and use tactile feedback to correct its actions. We then evaluate GPT-6 Astra across five established manipulation benchmarks along six capability dimensions. Despite competitive performance on several benchmarks-26.92\% success on RoboDojo and 76.0\% on RoboTwin 2.0-our analysis reveals a pronounced gap between semantic reasoning and physical execution, particularly in consequence-aware action planning, precision, and complex motion coordination. To further examine these limitations, we introduce LIBERO-GeoMotion, a new benchmark of geometry-constrained tasks that require precise pose alignment, coordinated translation and rotation, and anticipation of physical action consequences. GPT-6 Astra achieves only 11.1\% zero-shot success, exposing the difficulty of translating spatial understanding into physically feasible motion. Real-world experiments corroborate these findings: zero-shot execution is feasible for simple tasks, yet persistent deficits remain in motion feasibility, precise control, and physical safety, while substantial inference latency further hinders practical deployment. Overall, our results characterize the emerging embodied capabilities of general-purpose multimodal models and delineate the key challenges toward safe, efficient, and reliable robotic manipulation.

Active noise control (ANC) is an established technique for mitigating acoustic noise, successfully implemented in various commercial applications. However, the application of ANC to augmented reality (AR) glasses remains an emerging area, where a key challenge is the lack of a microphone at the user's ear. This paper first validates the necessity of virtual sensing techniques for this specific geometry and investigates the Auxiliary Filter (AF) method as a potential solution. We present a theoretical analysis of the method's directional sensitivity, enabling the prediction of the system's robustness when the noise direction deviates from the calibration angle. Simulation results confirm that while a fixed AF is effective under matched conditions, it suffers significant degradation under mismatch, consistent with the theoretical predictions. To address this limitation, we propose and evaluate a solution using a finite bank of auxiliary filters that are selected based on the noise source direction of arrival. The results demonstrate that this filter bank approach significantly recovers performance compared to a fixed filter, offering a practical alternative to continuous recalibration in dynamic acoustic environments.

Oddly Satisfying Videos (OSVs) can evoke strong viewer responses through repetitive motion, visual tactility, and ASMR-like sounds despite containing few explicit semantic emotion cues. This makes OSVs a challenging setting for Video Emotion Analysis (VEA), since most existing methods focus on semantic video content and under-model the physical sensory dynamics that shape viewer responses. To support Oddly Satisfying Video Emotion Analysis (OSVEA), we construct the Oddly Satisfying Video Dataset (OSVD), comprising 12,000 annotated 5-second clips. Each clip provides viewer-emotion labels under video-only, audio-only, and audio-visual conditions, together with explanations grounded in visual and acoustic sensory evidence. Building on OSVD, we propose PI-MLLM, a psychophysics-inspired multimodal large language model that integrates Modality-Specific Dynamics Alignment (MSDA) and Coalition-Based Audio-Visual Attribution (CAVA). MSDA uses auxiliary prediction objectives to align modality representations with visual motion and acoustic energy-onset dynamics. CAVA evaluates emotion scores across modality coalitions and applies Shapley attribution to identify the dominant modality and determine whether visual and auditory evidence is synergistic or conflicting. Experiments show that PI-MLLM improves both viewer-side emotion prediction and sensory-grounded explanation quality, suggesting the value of physical sensory cues to video emotion analysis.

VGL-stGen is a multimodal large language model adapted from a pretrained medical vision-language model using paired lung H&E and spatial transcriptomics with single-cell references. Training integrates image-expression and expression-cell-type pairs, and gene-conditioned pseudo-labels transfer transcriptomic cell-type supervision to histology images. One deployed checkpoint supports thirteen evaluated tasks spanning tissue and cell-type classification, gene prediction and conditional expression completion from combinations of histology, cell identity and observed gene expression. Task-specific decoding produces categorical labels, gene lists and structured expression levels. For conditional completion, fixing queried gene identities and predicting their levels autoregressively improves structured prediction. Controlled adaptation shows that restricting supervision to requested expression-level tokens can further improve image-conditioned completion. Image-permutation experiments indicate that correctly paired histology adds information beyond observed expression. External classification relies partly on computational references with shared annotation lineage, and some H&E sources were exposed during cancer training or model development. Within these conditions, VGL-stGen demonstrates how a medical vision-language backbone can learn from spatial transcriptomics and histology to connect tissue morphology and molecular states through shared generative modeling.

Cardinality estimation (CE) is crucial in database query optimization. Although recent advances have improved accuracy, deploying machine-learned CE models in dynamic databases remains challenging due to data updates and workload shifts. Retraining can be costly, but existing practices offer little guidance on when and how to update models, resulting in simple periodic retaining strategies that are suboptimal. We propose SWatcher+, a framework that adapts learned CE to dynamic workloads by monitoring data updates and query feedback. SWatcher+ selectively monitors high-impact subqueries for which wrong estimates lead to poor plan performance, and it proactively applies corrections to estimates during query optimization. This strategy enables immediate adaption to data and workload shifts without waiting for full model retraining, and carefully balances the cost and benefit of monitoring and adaption versus retraining. Our experiments show that SWatcher+ offers a better trade-off between query performance and overhead compared with existing approaches, making it a more practical solution for deploying learned CE in dynamic settings.

Asked to name a running shoe brand, language models say Nike. Asked to recommend one, they say Brooks. This paper asks where models learn that taste. Across 102 models and 42 brand categories, the brand a model picks when recommending differs from the brand it names in 26. The field moves together to a shared recommendation. The Named brands are market leaders, and the Picked brands are mostly niche and specialist. Three open training pipelines show where this forms. Pretraining already attaches the recommended brand to advice. Supervised fine-tuning teaches the model to answer and mostly leaves the pick unchanged. Preference optimization (DPO) teaches the model which answer is better, and the pick moves in all three pipelines, by 11 to 24 points. The preference data contains almost no brands. DPO moves the model's judgments toward a second set of associations even when the preferred brand is not in the preference data, and the effect reaches beyond brands. Asked to choose a sauce, models switch from ketchup to pesto. We do not know exactly how these preferences arise. We suspect they come from the judge models that decide which answers count as better during preference training. For brands, a recommendation depends less on what a model knows about them than on whether they fit this taste.

Floorplanning with rectilinear soft modules improves area utilization and wirelength by allowing modules to adapt to rectilinear polygon (RPoly) shapes. Existing methods typically construct rectilinear polygons through incremental refinement after obtaining a rectangular global solution, which confines polygon exploration to the neighborhood induced by the initial floorplan. This paper presents RPolyPlan, a unified framework for outline-free and fixed-outline floorplanning that directly incorporates continuously deformable rectilinear polygons into global floorplanning. To enable direct polygon optimization, we introduce a structured continuous representation and a differentiable polygon shaping model that dynamically optimizes rectilinear module shapes based on overlaps, making continuous shape optimization feasible for gradient-based global floorplanning. An augmented Lagrangian formulation robustly handles the coupled inequality constraints, provides theoretical convergence guarantees, and reduces dependence on manual penalty-parameter tuning. During legalization, minimum-cost flow and rectangular decomposition determine the target areas of subrectangles, and horizontal and vertical constraint graphs encode their geometric relations. The resulting convex legalization formulation satisfies the area, shape, separation, connectivity, and outline constraints while minimizing either the chip area or the displacement from the global floorplanning solution. Experiments on the GSRC, MCNC, and ICCAD 2023 contest benchmarks demonstrate that RPolyPlan reduces HPWL over the evaluated state-of-the-art methods by 7% and 6% in fixed-outline and outline-free experiments, respectively.

Reasoning about fine-grained placement constraints, such as support and containment, is essential for realistic 3D scene creation. It remains a significant challenge for existing methods that rely on simplified object representations like oriented bounding box (OBB), which are blind to the detailed geometry. To address this limitation, we introduce GALA, a geometry-aware language model with explicit point cloud perception for controllable object placement. Our model performs autoregressively by predicting the 6D pose of one target object at a time conditioned on the scene context and placement instruction. We utilize a two-stage training strategy: the first stage aligns geometric and textual modalities through pretraining tasks, and the second stage fine-tunes the model for placement. To facilitate this task, we also curate a multi-source scene dataset covering diverse room types and fine-grained furniture arrangements, which will be open-sourced for community benefit. Experiments on our benchmark show our model significantly outperforms baselines without explicit geometric reasoning. We further develop a multi-stage plan-place-verify agent pipeline that uses the model for text-driven scene generation. Project Page: https://xccelephant.github.io/paper/gala/

A model behind an API can be identified from its one-word answers to everyday questions such as "Name a sound" or "Name a poet". A model's profile records how often it gives each answer to each question. We attribute new answers to the model most likely to have given them. On a panel of 94 models, 40 answers identify the exact model 92.5% of the time, against 1.1% by chance. Profiles built through OpenRouter identified all ten models served by DeepInfra under blinded labels. A system prompt lowers accuracy by 6 to 16 points. We applied the method to 96 endpoints of 13 open models on OpenRouter, and 92 identify as the model they claim. Of the other four, one matches the claimed model with reasoning turned off. One serves Gemma 4 under the name Llama 4 Maverick: it names itself Gemma 4, and it is billed Gemma 4's token counts on every message. Two remain unresolved. Billing records also show context added to first-party models. Grok 4.7 is billed 1,247 input tokens for a one-line question that costs GPT-4o only 12 tokens, and five models state the current date without being billed for it. The questions come from a public census of model defaults, and the method costs cents per endpoint.