Toward decoupling the selection of compression algorithms from quality constraints

Data intense scientific domains use data compression to reduce the storage space needed. Lossless data compression preserves the original information accurately but on the domain of climate data usually yields a compression factor of only 2:1. Lossy data compression can achieve much higher compression rates depending on the tolerable error/precision needed. Therefore, the field of lossy compression is still subject to active research. From the perspective of a scientist, the compression algorithm does not matter but the qualitative information about the implied loss of precision of data is a concern. With the Scientific Compression Library (SCIL), we are developing a meta-compressor that allows users to set various quantities that define the acceptable error and the expected performance behavior. The ongoing work a preliminary stage for the design of an automatic compression algorithm selector. The task of this missing key component is the construction of appropriate chains of algorithms to yield the users requirements. This approach is a crucial step towards a scientifically safe use of much-needed lossy data compression, because it disentangles the tasks of determining scientific ground characteristics of tolerable noise, from the task of determining an optimal compression strategy given target noise levels and constraints. Future algorithms are used without change in the application code, once they are integrated into SCIL. In this paper, we describe the user interfaces and quantities, two compression algorithms and evaluate SCIL’s ability for compressing climate data. This will show that the novel algorithms are competitive with state-of-the-art compressors ZFP and SZ and illustrate that the best algorithm depends on user settings and data properties

Semi-automatic assessment of I/O behavior by inspecting the individual client-node timelines— an explorative study on 10^6 jobs

HPC applications with suboptimal I/O behavior interfere with well-behaving applications and lead to increased application runtime. In some cases, this may even lead to unresponsive systems and unfinished jobs. HPC monitoring systems can aid users and support staff to identify problematic behavior and support optimization of problematic applications. The key issue is how to identify relevant applications? A profile of an application doesn’t allow to identify problematic phases during the execution but tracing of each individual I/O is too invasive. In this work, we split the execution into segments, i.e., windows of fixed size and analyze profiles of them. We develop three I/O metrics to identify three relevant classes of inefficient I/O behaviors, and evaluate them on raw data of 1,000,000 jobs on the supercomputer Mistral. The advantages of our method is that temporal information about I/O activities during job runtime is preserved to some extent and can be used to identify phases of inefficient I/O. The main contribution of this work is the segmentation of time series and computation of metrics (Job-I/O-Utilization, Job-I/O-Problem-Time, and Job-I/O-Balance) that are effective to identify problematic I/O phases and jobs

Differential Localization of G Protein βγ Subunits

G protein βγ subunits play essential roles in regulating cellular signaling cascades, yet little is known about their distribution in tissues or their subcellular localization. While previous studies have suggested specific isoforms may exhibit a wide range of distributions throughout the central nervous system, a thorough investigation of the expression patterns of both Gβ and Gγ isoforms within subcellular fractions has not been conducted. To address this, we applied a targeted proteomics approach known as multiple-reaction monitoring to analyze localization patterns of Gβ and Gγ isoforms in pre- and postsynaptic fractions isolated from cortex, cerebellum, hippocampus, and striatum. Particular Gβ and Gγ subunits were found to exhibit distinct regional and subcellular localization patterns throughout the brain. Significant differences in subcellular localization between pre- and postsynaptic fractions were observed within the striatum for most Gβ and Gγ isoforms, while others exhibited completely unique expression patterns in all four brain regions examined. Such differences are a prerequisite for understanding roles of individual subunits in regulating specific signaling pathways throughout the central nervous system

3D multimodal dataset and token-based pose optimization

N00014-19-1-2571 - Department of Defense/ONRhttps://www.cs.bu.edu/faculty/betke/papers/Patel-etal-CV4Animals-CVPR-2022.pdfPublished versio

Tools for analyzing parallel I/O

Parallel application I/O performance often does not meet user expectations. Additionally, slight access pattern modifications may lead to significant changes in performance due to complex interactions between hardware and software. These issues call for sophisticated tools to capture, analyze, understand, and tune application I/O. In this paper, we highlight advances in monitoring tools to help address these issues. We also describe best practices, identify issues in measure- ment and analysis, and provide practical approaches to translate parallel I/O analysis into actionable outcomes for users, facility operators, and researchers

Valuations on lattice polytopes

This survey is on classification results for valuations defined on lattice polytopes that intertwine the special linear group over the integers. The basic real valued valuations, the coefficients of the Ehrhart polynomial, are introduced and their characterization by Betke and Kneser is discussed. More recent results include classification theorems for vector and convex body valued valuations. © Springer International Publishing AG 2017

Crystalline Assemblies and Densest Packings of a Family of Truncated Tetrahedra and the Role of Directional Entropic Forces

Polyhedra and their arrangements have intrigued humankind since the ancient Greeks and are today important motifs in condensed matter, with application to many classes of liquids and solids. Yet, little is known about the thermodynamically stable phases of polyhedrally-shaped building blocks, such as faceted nanoparticles and colloids. Although hard particles are known to organize due to entropy alone, and some unusual phases are reported in the literature, the role of entropic forces in connection with polyhedral shape is not well understood. Here, we study thermodynamic self-assembly of a family of truncated tetrahedra and report several atomic crystal isostructures, including diamond, {\beta}-tin, and high- pressure lithium, as the polyhedron shape varies from tetrahedral to octahedral. We compare our findings with the densest packings of the truncated tetrahedron family obtained by numerical compression and report a new space filling polyhedron, which has been overlooked in previous searches. Interestingly, the self-assembled structures differ from the densest packings. We show that the self-assembled crystal structures can be understood as a tendency for polyhedra to maximize face-to-face alignment, which can be generalized as directional entropic forces.Comment: Article + supplementary information. 23 pages, 10 figures, 2 table

Validating an infrared thermal switch as a novel access technology

<p>Abstract</p> <p>Background</p> <p>Recently, a novel single-switch access technology based on infrared thermography was proposed. The technology exploits the temperature differences between the inside and surrounding areas of the mouth as a switch trigger, thereby allowing voluntary switch activation upon mouth opening. However, for this technology to be clinically viable, it must be validated against a gold standard switch, such as a chin switch, that taps into the same voluntary motion.</p> <p>Methods</p> <p>In this study, we report an experiment designed to gauge the concurrent validity of the infrared thermal switch. Ten able-bodied adults participated in a series of 3 test sessions where they simultaneously used both an infrared thermal and conventional chin switch to perform multiple trials of a number identification task with visual, auditory and audiovisual stimuli. Participants also provided qualitative feedback about switch use. User performance with the two switches was quantified using an efficiency measure based on mutual information.</p> <p>Results</p> <p>User performance (p = 0.16) and response time (p = 0.25) with the infrared thermal switch were comparable to those of the gold standard. Users reported preference for the infrared thermal switch given its non-contact nature and robustness to changes in user posture.</p> <p>Conclusions</p> <p>Thermal infrared access technology appears to be a valid single switch alternative for individuals with disabilities who retain voluntary mouth opening and closing.</p

Majorations explicites de fonctions de Hilbert-Samuel géométrique et arithmétique

International audienceBy using the $\mathbb R$-filtration approach of Arakelov geometry, one establishes explicit upper bounds for geometric and arithmetic Hilbert-Samuel function for line bundles on projective varieties and hermitian line bundles on arithmetic projective varieties